It's old, I have it - What is it?

[Ulma Doctor]

Or make the missing pieces....

 

[mmcmdl]

Technicly , this is a toolmaker's gage base , denoted by the pins going thru the base . Without the pins , a surface gage base .

 

[WesPete66]

A question please.. What is the purpose of those pins? Also, how would the V-slot be used?

 

[middle.road]

Technicly , this is a toolmaker's gage base , denoted by the pins going thru the base . Without the pins , a surface gage base .

Ah, learn something new everyday.
All these years and with a few in tool chest I did not know that.
What about the ones with 'duck bill'(?) / ledge in the front for registering?

 

[mmcmdl]

A question please.. What is the purpose of those pins? Also, how would the V-slot be used?

Those pins are for checking parallelism between different surfaces . The v-slot is used for checking alignment off of round surfaces , such as mounting motors to gearboxes , checking tailstock alignment etc .