This came home with me last weekend, along with a bike I really wanted. (Pics of that one later.)
There is just a bit of info on Welter in the archives here and elsewhere. Pretty obviously it's a boom era gaspipe Italian, nothing subtle about it. No name on the dropouts that I could see...though I was mostly looking at the other bike.
Welter was apparently independent at first and later part of a group of companies called Garlatti. This must have been one of their better bikes; it does have Campy shifters and FD, which I guess are Valentino. Not yet being a Campy guy I don't know...aren't the shifters the same as Gran Sport and NR? The Campy name is prominently featured on two decals--the magic of advertising. The hubs are Normandy high-flange, with the coolest steel rims I have seen. Universal brakes, Pivo bars and stem, Magistroni cottered crank. The RD is now a Sunrace.
The cool thing about the bike is that under the paint it appears to be 100% chromed, and where the paint is scratched away the chrome even appears fairly polished. So it has the potential to be a pretty neat looking (if heavy) city daily rider. Of course, that's what my CL ad will say, the neat looking part anyway. Not sure yet whether to offer it as frame/fork (a C&V friend has dibs on the brakes) or if it's an easier sell complete.
So...for your viewing pleasure, and the benefit of the next person searching for info on the brand: