Hard to tell without a pic, but I'd guess its a 'DB Connector' or 'Game Port' connector.

DB-15 (DA-15 and DE-15)
Two DB-15 connectors are widely used. The larger, two-row female DA-15 is the game port on a PC, and the smaller, three-row, female high-density DE-15 is the VGA port.

The Game Port was used for joysticks, midi devices and other peripherals.

source

Answer from th3dude on Stack Exchange
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Walmart
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15 Pin Serial Usb
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Discussions

Can't find a 15 Pin Sub-D to Mini-USB anywhere
“15 pin d-sub” does not (uniquely) identify the electrically signaling which is being carried over the connector. So it is impossible to know what you need. I realize this comes as a surprise to many people, but not every thing which uses a given connector is compatible with every other thing that uses that connector. And the d-sub connectors have been around long enough to have accumulated all sorts of weird uses. More on reddit.com
🌐 r/CNC
14
1
June 13, 2023
15 pin to usb adapter help
If you like the joystick, get a serial to USB adapter or cable. Amazon has both male and female serial to USB cables for under $15.00. More on reddit.com
🌐 r/techsupport
2
1
September 26, 2023
DIY cable/ ALDL to 15 pin serial? - Third Generation F-Body Message Boards
There's no such animal as a 15 pin serial. There is 9 and 25 pin. The 15 pin connector on your laptop is for a monitor output. The best thing to do would be to buy a pre-made USB datalogging cable, such as the ALDU1+CABL1 combo from moates.net or the OBD1 cable from aldlcables.com. More on thirdgen.org
🌐 thirdgen.org
December 18, 2008
DB15 serial to USB for radio console programming
The connector does not dictate the interface. I'm assuming this is rs232? I don't know if there was ever a "standard" pin out for rs232 on a db15 connector. If you know the pin out of the radio's connector, your best option might be to make your own cable. For the PC side, I would just use a USB<->rs232 adapter. Using a pcie card won't really gain you anything. More on reddit.com
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5
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December 18, 2023
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Newegg
newegg.com › p › pl
15 pin serial to usb adapter | Newegg.com
April 30, 2026 - FT232RL USB TO D-SUB 15 PIN DB15 MALE ADAPTER RS232 SERIAL COMMUNICATION CABLE FOR SERVO DRIVER DRVGIII LINK TO PC (FT232RL CHIP) Cable length:(1.8M)
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Rocketry Forum
rocketryforum.com › forums › rocketry general discussion forum › the watering hole
15-pin to USB connector? | Rocketry Forum - Model Rocketry Forums
May 8, 2008 - Are you sure it is a 15 pin serial port? I know there are 25 pin and a 9 pin serial ports (the 25 pin was on older systems) You might be able to use a DB-25 to DB-9 adapter, then connect to a DB9-USB. No guarantee, just an idea. Look here at the Serial to Serial. https://www.cablestogo.com/product_list.asp?cat_id=101 John
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Alibaba
alibaba.com › showroom › 15-pin-serial-to-usb.html
15 Pin Serial to USB Cable - Reliable Data Transfer
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Alibaba
alibaba.com › showroom › rs232-15-pin-to-usb.html
Verified Supplier RS232 15 Pin to USB Supports Win7 OS | Alibaba.com
Discover RS232 15 pin to USB adapters with FTDI/PL2303 chips, USB 2.0 connectivity, and CE certification. Ideal for industrial & legacy device integration.
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Grand & Toy
grandandtoy.com › en › product › IMK34886_Zebra_-_USB__serial_cable_-_USB_to_15_pin_D-Sub_(DB-15).aspx
Zebra USB Cable - USB Data Transfer Cable - First End: USB | Grand & Toy
Serial Cables · Share · 25-62166-01R Also known as IMK34886 · New! Log in or create an account to see price and availability · Cable Type : USB · Connector Type on First End : USB · Connector on First End Details : USB · Compatibility : Symbol ADP9000 ·
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Alicat Scientific
store.alicat.com › products › usb-to-db15-232-485-serial-to-usb-converter-cable
USB to DB15-232/485 Serial to USB Converter Cable – Alicat Scientific
DB15(female) to USB 2.0 cable (6ft) for -DB15 devices Alicat instruments may be connected to computers USB ports by using our DB15 to USB conversion cables. These cables transmit serial communications however they will not power your Alicat ...
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Reddit
reddit.com › r/cnc › can't find a 15 pin sub-d to mini-usb anywhere
r/CNC on Reddit: Can't find a 15 Pin Sub-D to Mini-USB anywhere
June 13, 2023 -

Hi,

I am trying to connect a frequency converter to my computer to make it work with a software. Unfortunately the connector I need is from a company that has not replied to any of my emails. Would anyone know if anyone sells this specific adapter?

It is a 15 pin adapter to mini-USB

***Update

Sorry, it didn't seem to attach the picture I wanted to show, here is the link to what the adapter looks like, https://imgur.com/DRpi7nU

This is the website of the manufacture.

https://bmr-gmbh.com/zubehoer.htm

I have the diagram of the pins https://i.imgur.com/LPq3psK.png

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ShowMeCables
showmecables.com › by category › serial › db25 › usb to db25 male serial adapter cable - 6 ft
Serial Computer Cables - 6FT DB25 Male to USB Adapter | ShowMeCables.com
USB to DB25 Male Serial Adapter Cable - 6 FT
Add DB25 Port to PC | Drivers Included | 115.2K+ Data Transfer Rate | Windows Compatible
Price   $56.99
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Reddit
reddit.com › r/techsupport › 15 pin to usb adapter help
r/techsupport on Reddit: 15 pin to usb adapter help
September 26, 2023 -

I have an old Cyborg joystick with a 15 pin cable. I don't have a port for this on my pc. Is it worth getting a usb adapter? Any recommendations, experience or ideas are greatly appreciated

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eBay
ebay.com › 15 pin to usb adapter
15 pin to usb adapter products for sale | eBay
Get the best deals on 15 pin to usb adapter when you shop the largest online selection at eBay.com. Free shipping on many items | Browse your favorite brands | affordable prices.
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Third Generation F-Body Message Boards
thirdgen.org › third generation f-body message boards › tech boards › diy prom › diy cable/ aldl to 15 pin serial?
DIY cable/ ALDL to 15 pin serial? - Third Generation F-Body Message Boards
December 18, 2008 - There's no such animal as a 15 pin serial. There is 9 and 25 pin. The 15 pin connector on your laptop is for a monitor output. The best thing to do would be to buy a pre-made USB datalogging cable, such as the ALDU1+CABL1 combo from moates.net or the OBD1 cable from aldlcables.com...
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Reddit
reddit.com › r/vintagecomputing › db15 serial to usb for radio console programming
r/vintagecomputing on Reddit: DB15 serial to USB for radio console programming
December 18, 2023 -

I am trying to find a way to program an old radio console, a GaiTronics CommandPlus. It interfaces via a DB15 male serial connection. I cannot find a pcie DB15 serial card. Pcie is the only interface other than USB available to me. The easier option though is a DB9/DB25 to USB cable. Then using a DB9/DB25 to DB15 adapter. Looking at old product listings it looks like the radio interfaced with a DB9 to DB15 cable.

Also super annoyed that search results for DB15 lead me to gameport or VGA results. Even filtering out those terms results are not what I am looking for.

Any Amazon products available to do the job? Or information for me to fashion my own DB9/DB25 to DB15 cable? Yes purchasing or finding an old computer is available but comes to "does it have a DB15, if not then I'll need to adapt to DB9/DB25."

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AliExpress
aliexpress.com › w › wholesale-15-pin-male-to-usb-adapter.html
15 Pin Male To Usb Adapter
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Straight Dope Message Board
boards.straightdope.com › factual questions
15-pin serial adapter for USB not possible? Help! - Factual Questions - Straight Dope Message Board
July 30, 2001 - I recently bought a used NEC MobilePro H/PC, and I love it. Getting it to sync with my Macs has been a challenge, though. I’ve been able to do it so far by running Virtual PC on my PowerBook 3400, which has a high-density 15-pin serial port (needed for the sync cable) on the back of it… but it would be real handy to be able to perform the same feat with my G4 at work, since I don’t usually bring the PowerBook in to my office.
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ShowMeCables
showmecables.com › by category › serial › db9 › usb to db9 male serial adapter cable - 1.5 ft
Serial Computer Cables - 1.5FT DB9 Male to USB Adapter | ShowMeCables.com
USB to DB9 Male Serial Adapter Cable - 1.5 FT
Add DB9 Port to PC | Automatic Handshake | 230kbps+ Data Transfer Rate | Windows Compatible
Price   $40.99