Bergeon 30112 Micrometer

[sean30ber]

So I purchased this micrometer and being vintage it had no instructions. Im new to precision tools so here is my issue. The plates have a cut so they will slide across the table nice and smooth. With this one, the shaft rotates the measuring plate so the table cannot be used. Am I not doing something right? am I missing something?. Ive seen several of these and as the tub is twisted, the shaft moves in and out without rotating. I cant find any posted manual for this. Thanks for the help

 

[sean30ber]

Was locked up with old dried oil. Some one dip, a good cleaning and she is smooth as silk.