I just joined the forum having stumbled across it while searching google for some info. I chanced upon a recent bike restoration project (started yesterday) but quickly ran into trouble once I discovered my Top Tube was rusting away from the inside out.
ANYWAY, the frame was fitted with Mercier front forks but the only other markings on the frame are the Vitus rear dropouts and a serial number M 58098 on the bottom. It was originally my fathers bike and he bought it in the late 80s and thought it was a Mercier he had bought but it had even been repainted then.
The tubing is oval and is brazed together as opposes to butted. The seatpost is also oval (aluminium) and there is no seat clamp just a grub screw on the rear of the seat post. The rear half of the frame was originally chrome but the rest is plane steel.
I have not found anything like it on the internet anywhere and have emailed Mercier but fell that it could be next week before I hear anything back from them. In the mean time if anyone has any leads I would be keen to hear. Based in Ireland and its 23.30 but will check back soon