This lot of brass ring-back buttons had some real gems in it, the nicest of which I've already put on my MFSC Shore Coat (pics at a later time).
Work and uniform jackets often came with these type of buttons so that one could easily change the standard ones for the ones supplied by the company they worked for or branch of military they were in.
Included in this lot were some anchors, ordnance symbols, "pompiers" (fire brigade),
as well as a bunch that seem to have been from a local university.
The bomb with the flames coming out of it is the ordnance symbol, also note the small bomb and anchor on the back of the button on the right.
I had never seen the small cross instead of the ring before, and while it looks very cool I must say it isn't as easy to use as the ring is.