Did Shure ever sell a stylus force gauge with the model number SFG-1?
Yes, but only as part of the Shure C/PEK-1: Cartridge Performance Evaluation Kit - Version 1. The SFG-1 was not sold as a stand-alone accessory.
The SFG-1 (Stylus Force Gauge) was a dynamometer, made in France, supplied by Carpano & Pons. It was a precision device that measured up to 5 grams with increments of 0.1 grams, machined of metal, with a dappled gray "hammer" finish. The read-out in grams was indicated by a needle that rotated around a circular dial. The SFG-1 was housed in a dark blue case, with a single brass latch, and a red cloth interior.
If purchased as a replacement part in the mid 1970s, the SFG-1 was priced around $125.