I don't know what that micrometer was used for. But what I do know:
Micrometers with V-shaped anvils are (most often) used for measuring items with an odd number of vanes, or fins, or flutes, or whatever. For instance think of a shaft with three equally-spaced flats running the full length of it. You couldn't measure the shaft diameter with a regular mic, you would need a V-angle mic with anvils set at 60 degrees from one another. This is the most common V-angle mic.
The anvils on your mic appear to be set at 108 degrees from each other, which would be for measuring a 5-sided item. Perhaps a small fan rotor blade or the like? Hmmm.