The roller coaster history of this series:
Out of the 12 initially introduced models, 7 were identical to 7 of the 12 models from the 1989 Sears Set;
Production moved from the USA to China in 1990;
In 1991, 3 models got replaced, while 1 was discontinued entirly;
The 'old' plastic was replaced by the 'new' plastic in 1992.
As a result, 11 out of the 15 different models/colours have been produced in both the old and new type of plastic, the other 4 in old plastic only, sold at first in 1989 on remains of the white cards, after that on ©1989 'MADE IN USA' cards which got replaced by ©1990 'MADE IN CHINA' cards.
The 2 different types of plastic can be distinguished by the sound they make when the Stablemate is placed on a hard surface, or by gently rubbing their hoof soles close to your ear, the old, softer cellulose acetate has a more 'thudding' sound, while the new, harder polystyrene has a higher, more 'zingy' pitch to the sound. Also, old plastic is slightly heavier and can be prone to shrinking, often causing a vinegar-like smell, while the new plastic is much more stable.
On this page, if applicable, the old and new plastic ones are next to each other. Most of the new plastic models tend to be slightly darker in colour than their predecessors, but that's not always the case. The way they applied the dapples also changed, so they look different too.
And then there's what I refer to as 'teary' eyes. Roughly around 1988-1990 (so already at the end of the original first series), a lot of the Stablemates got their eyes glossed in a rough way, as if they have teary eyes, like in the Sears 1989 set, but the singles had it just as well. The first of the new plastics seem to all have matte eyes, but starting 1994, eyes got properly glossed, only the eyeballs, and that's what I refer to 'glossy' eyes, like in the JCP 1994 set. Not all got the treatment, so not having them doesn't mean they weren't from that period. Mentioned periods are based on my own observations, I haven't seen any comments around the subject except for the Sears 1989 and JCP 1994 sets.
Since all models on this page are bought 2nd hand, unless some package is referred to, the 7 models mentioned above in old plastic, if old enough, might actually be a Sears 1989, although that's less likely.
5020 1976-1990
old plastic only, teary eyes
from ©1979 white card with #5600 sticker >> 1989
bay, teary eyes
5024 1976-1990
old plastic only, teary eyes
from ©1979 white card with #5600 sticker >> 1989
bay, teary eyes
5022 1976-1994
old plastic >> 1976-1992
from ©1979 white card with #5600 sticker >> 1989
chestnut, teary eyes
The old plastic #5019 Citation on the left is sealed on a ©1989 'MADE IN USA' card, the new plastic one on the right on a more common ©1990 'MADE IN CHINA' one.
According to the Breyer catalogs, the #5019 was introduced in 1991, so technically, a ©1989 #5019 could only excist if they used an outdated card. However, it's quite likely that the #5019 was already introduced late 1990, inbetween annual catalogs. It's also very likely that they still used the ©1989 cards during the first part of 1990, making it quite plausable that my older one is from the period in 1990 between the two introductions. Looking at how rare the ©1989 cards are, I can't imagine it took long before they ran out of them and started using the newer ones.
note: I checked the weight of both sealed cards to determine whether the Citations were old or new plastic. The difference in this case is over 50 grams/1.76 ounces.