I think I actually own the prototype of that.
My old Kity 419 had an interesting history. Original an eval/review unit, apparently it featured in a magazine. It had two owners before me, and I've now passed it on to Rafezetter. I'm using the sliding table with my TS200, and the rail has that fitting. I believe it was made by the original owner for a magazine article.
The rail isn't on the saw presently, but I can put my hand to the "stop" almost immediately, as it's safe in a tool drawer. I'll have a look later and post a comparison pic...
E.
PS there were a couple of other mods done to it when I got it, I think mainly relating to DX. Will try to remember.
PPS: It _is_ a useful thing, as long as you have the space round the saw in the first place. I'd prefer the rail to be another 500mm or so longer, to handle small sheet stock better, but, IIRC, Kity only sold it in the short 1200m or (stupidly long) 3m alternatives. The long one had extra legs, but the saw and carriage is unsuitable for working with 8x4 sheets, etc, so I struggle to see the point. I'm guessing Kity didn't sell many units!