The arched stamping has never been repopped to my knowledge. IMHO it's worth $100 tops. As others have said the value is in the pulley and only a purist restoration would "need" one like it. If the alternator were in better condition and the orange ink stamp was still on it it would bring the value up a bit.
Just this old man's opinion,
'66 GT350H-3 time cover car - Car Craft July'77,Modified Mustangs and Fords Feb2011 ( w/article), Mustang Monthly June 2014. Bracket raced by me for the last 44 years. Yes it is a real one.
'68.5 R code GT fastback
'67 Ranchero 408W -427 glass hood
'78 F350 "Oleynik" car hauler
Ford Experimental parts collector