L S Starret 1" Micrometer

[racecar builder]

Have the last micrometer for 1 2 and 3 inch set.

Relative is loaning me this Starret T1230.

What is the knurled ring where the locking lever is on one of the other micrometers?

I don't like to guess?

 

[BogusSVO]

The barrel lock of the mic, has a ring not a lever

 

[racecar builder]

Thank you BogusSVO

Looks like Starret still makes them.

http://www.starrett.com/metrology/product-detail/T1230XRL#Downloads

Anybody know where they hide the .PDF manuals?