Originally Posted by T-Mar

A stamped dropout with integral hanger on a frame devoid on braze-ons usually indicates a 1970s boom era model that is mid or high range. The spindle looks to be cotterless and if original, would corroborate this. The only thing I see that looks out of place is the rear triangle (and I"m not talking about the bend). Typically, the stay ends would chromed, like the fork, but this does not appear to the case, based on what I can see.

A Mercier model from this era with Reynolds 531 would be the model 300. The best way to determine the tubing is probably the seat tube diameter. Being a french frame, it should have the smaller, 28mm outer diameter seat tube. The inner diameter for a Reynolds 531 butted, 28mm seat tube was typically 26.6mm, though a thinner tube with a 27.0mm inner diameter was also available.