To my knowledge, an Italian firm (as stated above) but certainly not existant any more. Loved their kits, actually, esp their 1:12 F1's! Bit more work than Tamiya counterparts, but lovely. Yeah, those bike chains... what a memory to bring back! If you have this question, obviously you have a kit you're looking at... Which is it? Maybe somebody can tell you more.
As far as their Italeri link - I think that their bike dept. (at least) was bought by Italeri. Have not built one of Italeri's latest bikes, so I can't comment on what their quality is like, relative to Protar's... But if I am correct, it should be good. And maybe you can't go by the chain assembly alone, since they might have changed that since I last built a Protar bike. (If it involves putting the chain together (so that it looks very real) by building it in 3 layers and melting the ptrotruding parts keep it all together, it's a dead giveaway.
Additionaly, I think Revell has their 1:12 F1's. I saw some Revell boxes come out with the exact same models inside a while ago. (Older type F1's)
Hope I haven't misled you more than anything!