As a general rule "write such that someone which doesn't know and/or write such that someone in 10 years will know what it is"*.
For the sake of others playing along it appears it is an unofficial third party... either mod or wholesale replica (the article and quoted statement from sega are not specific here,
https://bootleggames.fandom.com/wiki/Treamcast reckons modded device in a custom shell which is where I would have bet given the time it all happened in -- it only being in recent years that FPGA emulation/simulation/replication has hit the commercial world, and I am still waiting on custom remade chips) with a screen (usually a tweaked one that the PS1 car adapter kits used) to make it portable. I then find the infringing claim somewhat dubious (you can dispose of items however you like and all that, however the modded firmware could trouble something, somewhere -- this was still mod chip country so custom firmwares was not the thing it is today) but hey.
*in this case I missed it at the time but even if I hadn't then it has been some 16 years
https://www.geek.com/games/sega-slams-the-door-on-unofficial-treamcast-551175/
Don't know if I would do this as anything other than a piece of history. At this point you can probably get 50 times better results doing something yourself with modern gear.
