I've never heard of a Merlin having an Italian threaded bottom bracket, or an ovalized top tube. I'd be highly skeptical of the seller's claim that it is a Merlin.

I wonder if perhaps it was built by Litespeed, to another brand's specifications, and relabeled under that brand name? For example, both Merckx and Basso contracted Litespeed to build their ti frames, and both brands used Italian threaded bottom brackets on their steel bikes. (I don't know if the ti frames also incorporated the Italian threading.) However, that does not look like either a Merckx or a Basso ti, as I recall. Did Tommaso ever have ti frames in their line up?