This model was issued from 1994-1997 with her matching Nursing Foal, both sculpted by Chris Hess. Wow, I didn't realize the set was that old! They were regular run item #3180. Evidently they got in on the Great Bi-Eye Project of 1997 (thanks for that info, IDYB!), but my set doesn't have bi-eyes.
I think the Thoroughbred Mare is one of Hess's more underrated sculpts. I like her sweet expression, and her foal is a cutie too! And it probably says something that I like her, because she's one of the few Hess molds still remaining in my collection.
It's unfortunate that the set doesn't get used more often (although the various regular run releases ran for a combined 22 years), because I'd definitely have more sets than I currently do. I'm still waiting for them to show up in the Vintage Club in glossy alabaster! Mmm. I also wouldn't mind seeing them at this year's Breyerfest, although that's probably a lost cause. I can only hope!