You are correct -- mea culpa! After digging out my stash of catalogs, Beacon Cycle and Supply Company did indeed import Merciers (and Jeunets, too).
Question remains: the catalog makes no reference to Campy-equipped 300s? Did Beacon upgrade them, or was it common practice for LBS's to selectively upgrade for a particular market?
Several have emailed asking for pix -- will try to dig out archived images from the original eBay ad from a couple of years back and forward them. This weekend, I'll try to knock out a digital photo shoot of the Mercier for Dale's CR Mercier page (as well as some images of my just completed ca. '80 Peugeot PKN-10 for the Peugeot page).
Cheers,
Ian Kersey
Wmbg, VA