I think you might have 75 mg delayed-release
diclofenac sodium made by Purepac. The pill is described as white, round and enteric coated with the Purepac logo on one side and 551 on the other side.
Diclofenac is an anti-inflammatory.
The Purepac logo is hard to describe - it's sort of a fancy R. Others have described it as a cursive P with a dash, the breast cancer ribbon with a hyphen, a fish with a fin etc. And now you call it "half figure eight with a dash." Sounds good to me!
More info re diclofenac:
http://diclofenac.drugs.com/