Hi guys. This is my father's bike.
Can anyone recognize or give any hint on the brand of this frame?
Stickers seem to be offbrand. Paint work appears original. Located in Europe. Probably 80's ou early 90's?

The split downtube is certainly unique. I've seen one or two frames like that, though their names escape me. I'm confident someone more knowledgeable than me will come along shortly. Good looking bike!

Paletti had some split seat tube frames, but they used a different setup IIRC.

None of the others I have seen have the dropped seat stay attachment - Saxon, Rigi, Paletti, Mecacycle

Edit: Could the stamp on the BB be from Racord Gargette Freres?
"RGF" French bottom bracket shell?

You're right. It's the same logo!

Puch had the Mistral Bergmaschine, but that one also was missing the dropped seat stay treatment. Never seen one like this. Cool bike!

Crazy build on a crazy frame! Parts bin build or gradually updated over many years. Mismatched wheels. Controls and seat are newer. Crankset looks age appropriate. Check out the single bolt style seat post, which is - just totally out of left field, usually found on cheap bikes or antiques.

If I had that frame I'd try to do anything I could afford with it too, it's really cool

yep it's unlike any other "twin seat tube" I ever saw!
Curious to see how the FD is mounted as well as other details (like the DOs and fork ends. brake bridge, etc.) some things are sort of "earlier" like the RGF BB shell and fishmouth stay details, but I think both brakes are recessed Allen-head bolts plus the WB bosses and cable routing are a "bit later" in fashion. Might even be a custom one-off frame

I wonder if the seat tube was reinforced with a shim (something I'd want to see with those "shot-in" seat stays!) and if so maybe required a smaller size seat post?

Threading in the BB would narrow it down. Maybe something offbeat and Swiss?

The knurling on the lockring may indicate thread spec. While the crank arm is Campagnolo, the lockring is not, as Campagnolo did not knurl their lockrings. If it's a TA lockring, that knurling pattern would indicate English thread. But if it's a Nervar lockring, it would indicate French thread.

From Sutherland's 4th Edition.

I believe Freschi also made some split seat tube bikes. The one below also has dropped seat stay attachment; but a different style than the subject bike. If yours was a Freschi, though, I can't imagine it wouldn't have engraved "F"s on it in several places.

More photos of this Freschi here: https://cicli-berlinetta.com/product...oad-bike-58cm/

Rigi made frames like that, probably the best known.

A couple more photos. Can't find any imprint on the frame...

pix of the components are not so helpful, but what ARE is that the BB is a Stronglight and appears to have 6 notches in the lock-ring, so you could read the rest of the markings and find out if it's (as likely to be ) French threading.
The other detail is the dropout, which I think (and JDT can confirm, cause he knows his DOs!) may be a Shimano "UF" semi-vertical?

You can take the QR nut off and see if there are Brand stampings on the face of that DO

The rear dropouts are either Shimano UF or Gipiemme 1800AX. The differences are subtle, and not obvious in the OP's picture, but I'm leaning toward Shimano UF.
Shimano UF:


Gipiemme 1800AX:

Of the two, the UF has this bit:

Can I get a close up on how the front derailleur attaches to the skinny seat tube?

I know there is a single hole facing outward

Mairag out of Switzerland ??

Polcholpek (? spelling) out of France ??

I think both of those small companies made this style of bike. It was always a freakshow of a design intended to catch the novices eye and pocketbook. Ultra-short wheelbases provide no real advantages and after the initial honeymoon, most everyone moves on to a more "regular" design.

Can't read anything...

Huh! So the FD mounting bolt goes right through the RH seat tube? Not sure if I like that since there's not a lot of material in either of those skinny twin tubes, but if it hasn't failed so far...
Also hard to judge from this pic but perhaps the places the FD close enough to the rear wheel that you could experience some rubbing, from normal flexing. Another thing that wouldn't be "nice" if it got serious!

Due to its color, I want to call it the Huffy Aero Criterium. No such animal actually exists, but it could...
Phil

It might be a Fowler or an America.

I was going to say that it could be a rebranded "Mecacycle Turbo" bike, which were made in France in the late 80's. It being their top of the line "Turbo" bike, had the split seat tube like that, but I think all the Turbo bikes had lugless fillet brazed joint construction (Made with very lightweight Supervitus 980 tubing.). Not lugged, like the OP's subject bike.