So thanks to Juvela for sleuthing these frame parts, we may have Nervex 15/158 lugs and brakebridge but Agrati stamped dropouts: which country of origin would that point to?
Couple more questions: is the BB shell also Nervex (does not appear to be either the "Pro" or a "158" model)?
What make is the forkcrown? (also wouldn't hurt to have measurements of the fork blades across the short and long axis, they don't appear to be typical of Reynolds to my casual glance)
More vital than ever is the threading, seat post size and ODs of the main tubes to rule out and in certain possibilities.
Minor detail: I think the headlugs on the La Perle are actually the 86bis/158 model (see pic from Velobase)
