The rarest is the red MV. The next rarest are the red MM and the blue WW, WC, WH. Then blue WU, HX and red YC, XC. The rest are fairly easy to find. Reds are a lot more common than blues.
Error OPAs are worth a little more. There is a good example at the end of this page.
Tokens used for rationing during World War II
There are 30 different red tokens and 24 blue ones.
They are all vulacanized fiber (celluloid) and 16mm in size.
Blue ones read: OPA Blue Point 1 (with two different letters)
Red ones read: OPA Red Point 1 (with two different letters)
**SPECIAL** Complete set of the above blue OPAs $19.95
Canada Meat $2.00
ERROR OPA'S
Error - Off Center, Blue CT $3.00
Error - Off Center, Blue UU $3.00
Error - Off Center, Blue HY $2.50
Error - Off Center, Red HT $3.50
Error - Off Center, Red VX $4.50
Error - Off Center, Blue YC $2.50
Error - Way Off Center, Red TH $6.50
Error - Way Off Center, Red UX $6.50
Error - Way Off Center, Red TY $6.50
Error - Way Off Center, Red VU $6.50
Error - Way Off Center, Red YX $6.50
Error - Double Stamped, Red VU $5.00
Error - Double Stamped, Red YT $5.00
Error - Double Stamped, Red YU $5.00
Error - Double Stamped, Red TY $5.00
Error - Double Stamped, Red YT $5.00
Error - Double Stamped, Blue CV $5.00
Error - Double Stamped, Blue CX $5.00
Error - Double Stamped, Blue TT $5.00
Error - Double Stamped, Off Center Red (Stamped too far off for letters to show) $10.00
The following is an example of an error OPAs. The pictures were sent to me by Dan Orbeck. As you can see OPAs can be struck, by mistake, more than one time. They are also not always centered when struck.