Just picked this Sun Tach (and matching transmitter) from a swap meet and I can't seem to find any info to date it. It's a model RB1, and uses an EB transmitter. It has a br*** face which is throwing me off for what the date of it could be. So what year do you think it's from?
It appears the RB 1 is the same as the RC 1 except for being Br***. I guess that is what the B stands for in the catalog number. There is an RC 1 on ebay, buy it now for over 200 without the transmitter.
Check with Ron at Williamson's Gauge in Arkansas. Phone number 479 369 2551 They do a fair a mount of Sun Tachs.