Guess the marque
 

Recently acquired this frame, and it came with a little back story. The previous owner was an amateur racer in the 80s. They presumably rode for a Redline dealer and had the bike repainted with Redline decals added.
I know who made the frame; let's see if anyone can guess.

Only hints are that it has a 26.4 ID seat tube, Italian threaded bottom bracket, and is not a Redline.

https://live.staticflickr.com/65535/...514e1aea_b.jpg

https://live.staticflickr.com/65535/...60394c8a_b.jpg

https://live.staticflickr.com/65535/...0dd3c446_b.jpg

https://live.staticflickr.com/65535/...3d6a6c34_b.jpg

https://live.staticflickr.com/65535/...5031da6f_b.jpg

https://live.staticflickr.com/65535/...c1c44f80_b.jpg

I love a good mystery...but can we have some more clues, such as:
what's the frame tubing?
What make are the semi-vert DOs?
Is that fork carbon fiber, aluminum alloy or what?
Is the Stronglight Delta HS a FR or Brit threaded item?

Fork is steel with an Everest imprint on the underside of the crown, though I haven't seen this casting before.
Tubeset is Super Vitus 980.
BSA Stronglight Delta headset.
That should help somewhat.

Mercet

Great guess. The treatment of the seatstay and chainstay ends at the dropouts and seat tube is very reminiscent of Mercet. But it is not him.
Take note of the crimp in the seat tube allowing tire clearance with very short chainstays. There is a marque known for short chainstays in that part of the world.

Mécacycle? Looks very much like their Turbo model, aside from the split seat tube.

https://cimg2.ibsrv.net/gimg/bikefor...a4022a76ab.png

Frullani?

Ciocc?

Huffy?

Shwin?

Fred?

Huffente?

BINGO!! We have a winner.
Mecacycle Chrono model from near the end of the company's lifespan.
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​​​​​​The rest of you cracked me up 🤣

very interesting, had to look up the story of Mécacycle and the Chrono model. Surprised that this had Ital BB shell and BSC fork threading but still metric tubing. And apparently most Chronos were built with (assuming metric) Columbus tubing. Fillet brazing was a hallmark of this St. Etienne-based construteur (SP).

Mecacycle actually let you choose which threading you wanted. See the note at the bottom of this page from the 1987 catalogue. I've seen Mecacycles with many different thread standards all over the internet.

https://cimg3.ibsrv.net/gimg/bikefor...16af65fd9f.jpg

They look like Shimano UF:
https://cimg2.ibsrv.net/gimg/bikefor...b148017d8e.jpg