Federal Indicator Base H28107310 .07” Travel.

Listing is for one single indicator base. Multiple bases for sale, all in similar condition. Movement is very smooth. I’ve never seen a base like these, they appear to be some sort of depth gauge. Some have letters and number scribed on them. Condition is used, but all still have wax still on them. Indicator in the picture is sold separately. Any questions Ill do my best to answer them. Thanks for looking!