I have no idea, but, I'm gonna guess: Pietro Beretta-Full-Silver Pigeon. I've owned Beretta's and have never seen anything like this.

 

pb is the periodic chart symbol for lead. F = Full, SP I think is for their Optima plus line of chokes.

So your chokes if Full for lead (probably lead only).

 

This might help as well:

http://www.berettausa.com/en-us/how-to- ... hoke-tube/

 

From kjs's link:
"Mobilchoke choke tubes will be marked PB or ST and the degree of choke. If the choke tube is steel shot compatible it will also be marked SP ."

 

If the choke tube is steel shot compatible it will also be marked SP and When using steel shot, we suggest that you only use choke tubes marked with the "SP" (Steel Proof) identification on the side, and that you use the most open choke system possible. To this end, any chokes up to and including a Modified constriction are suitable for steel shot.

Beretta steel proof statements are contradictory.

 

It means:
Pietro Beretta-Full-Steel Proofed
PB-F-SP