Hi guys, a bit of help here please.
I just got a 3-4" micrometer on fleabay for £6 + p+p.
its a german make, FEINMESSZEUGFABRIK.
it looks to be in excellent condition, see pic

however, when I test it using the 3" standard I'm half a thou out and I can't figure out how to adjust the darn thing.
the only adjustment I can see is to take up wear in the thread.
I googled adjustments and all I see is turning the barrel using the spanner in a hole in the barrel.
guess what, this hasn't got a hole.
on the inside of the barrel there s a collar with two holes,

is this an adjustment or does it just hold the whole shooting match together, I don't want to mess with it until I know what I am doing.
has anybody got any ideas.
cheers
Roy.