This little guy was designed by me (GutBomb) and Ron of Ron's Computer Videos to provide easy access to the DB9 port used for some of Ron's little boards that allow easy access to the video signal from many classic Macs to output to an external display.
Check out Ron's video on this thing here:
Also included is a handy-dandy micro SD card slot you can use in conjunction with an internal hard drive emulator of your choice!
These are the micro SD card extension devices that this was designed to use: https://www.amazon.com/gp/product/B09CKRDFTH/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
It should work with pretty much any DB9 connector.
I just created a new variant of this that has a full size SD card slot with no DB9. You can get the full size SD card extensions here: https://www.amazon.com/dp/B07SYFCG17?psc=1&ref=ppx_yo2ov_dt_b_product_details
If you enjoy my stuff and feel like showing your support in a financial way, please feel free to donate to me on my ko-fi page. I make this stuff for fun, but a little scratch can make it even more fun :D
https://ko-fi.com/gutbomb57331
The author remixed this model.
I adapted adam.l11's fantastic SD card extension holder to fit my SE and SE/30 expansion slot bracket.