Gruen Precision VeriThin

[richiec]

Picked this Gruen wristwatch up in a box of stuff when buying a pocket watch at the local antique shop. I had a main spring in another box of stuff but am wondering, the BestFit catalog shows the staff as a 392 and my main question, is the staff riveted or friction? It will run with pressure on the cock but the top of the staff is broken off, the jewel appears in good condition.

 

[psfred]

So far as I know, all Gruen Veri-Thin balance staffs are riveted. Should be obvious when you take the hairspring off at any rate.

Gary Hurt will know more, he's the Gruen guy here.

Peter