Before the internet made visual identification of R-390A manufacturer variants relatively straightforward, collectors buying at hamfests, surplus sales, and eventually through online auctions faced a recurring challenge: how do you tell a Collins from a Motorola, an EAC from a Stewart-Warner, when the nomenclature tag might be mismatched or missing entirely? Randy Stout addressed this problem head-on by compiling the R-390A “Spotter’s Guide” — a systematic visual reference that became an essential tool for the collecting community.

The Identification Problem

The R-390A was manufactured by more than a dozen contractors over a production span of roughly thirty years, from 1954 to 1984. While all were built to the same Collins-designed specifications, each manufacturer introduced subtle differences in construction details — variations in component placement, mechanical hardware, chassis finishing, and assembly techniques that became fingerprints for the knowledgeable observer.

Complicating matters, the military’s standard practice of depot-level maintenance meant that modules were routinely swapped between receivers of different manufacture. A receiver might carry a Collins nomenclature tag while containing an EAC IF deck, a Motorola RF assembly, and a Cosmos PTO. The widespread practice of tag swapping — both in service and in the civilian surplus market — meant that the nameplate on the front panel was often the least reliable indicator of a receiver’s true identity.

Building the Guide

Randy’s Spotter’s Guide drew heavily on the production data painstakingly compiled by Tom Marcotte, N5OFF, who had spent years assembling contract numbers, manufacturer details, and quantity data for the entire R-390 family. To this foundation, Randy added the practical visual identification details contributed by collectors across the community — the kind of knowledge that could only be accumulated through handling many examples of each manufacturer’s production.

The guide catalogued identifying features that an experienced eye could spot from across a hamfest table or, critically, from photographs in an online listing: the number and placement of fuses, the presence or absence of dimples on mechanical filter covers, differences in chassis plating and finish, variations in wiring harness routing, and dozens of other telltale details. Each manufacturer’s production had its own constellation of identifying characteristics, and the guide organized this knowledge into a practical reference.

Impact on the Community

The Spotter’s Guide became an indispensable resource for long-distance purchasing. As the R-390A market increasingly moved online — first through mailing list classifieds and later through auction sites — buyers needed to evaluate receivers from photographs alone. Randy’s guide gave them the tools to look past a potentially misleading nameplate and identify what they were actually buying, right down to the contract period in some cases.

For collectors focused on assembling matching-contract receivers — where every module comes from the same manufacturer and production run — the guide was especially valuable. It allowed them to verify module authenticity from photos and to identify mismatched components that might indicate a less desirable mix-and-match configuration.