A couple notes about the label on the side of the box....
1 - The date of 8/78 in not the date of manufacture but looks like a date of when the tach's (4 of them) were received.
2 - The part number on the label "SC 1458" is a Bridgestone/Rockford number.
I've got a handle bar leather tool bag (part # SC 1294) made by Starlite Leather Products. It's possible that the manufacturer of these tach's supplied them to Rockford for resale like Starlite did the tool bags.
If anyone has one of the "Accessories Catalog", maybe they could check and see if these are in there with that part number.....