This stem was very likely made by Potomac; the only basis for the attribution is the etch, which is Potomac’s. The etch is on a flared bowl with a six-sided stem and wafer.
There has been no indication that the etch has been used on any other companies' blanks (decorated by Potomac) and no indication the etch followed the Sloan’s to Sloan Bros in Lonaconing.
Without catalogs, advertisements and dump artifacts it has been difficult to attribute items to Potomac with certainty.
