Having some free time of late, I typed up a list of known Jawa proofs and some numbers that may possibly exist. I would appreciate some assistance, just in case my numbers are not accurate.
SW 12 Back (3)
*Square bottom and top with a blank back
SW 12/20 Back Mockup (one-of)
*Only one known example and uses the a common 12 back proof (per above) - LP Logo and white price square covered/airbushed out
SW 20 Back Cromalin (Fett Offer) (one-of)
ESB 21 Back (Secret Figure Offer) (5 – 10)
ESB 31 Back (5 – 10)
ESB 41A Back (2 – 5)
*Common proof and Round Corners / No Punch
EBS 41C Back (Survival Kit Offer) (2 -3)
ESB 45 Back (Display Offer) (5 – 10)
ESB 47 Back (one-of)
Round Corners / No Punch
ESB 48A Back (1)
Round Corners / No Punch
ESB 48C Back (2)
Round Corners / No Punch
Revenge 48 Back (20 – 30)
Revenge 65 Back (one-of)
ROTJ 65A Back ( 5 – 10)
ROTJ 65C Back (Emperor Offer) (2 -3)
Round Corners / No Punch
ROTJ 65 Back Cromalin (Emperor Offer) (one-of)
POTF 92 Back (<5)
**Available in common, uncut and production like form