I thought the change was in 94, which is why i'm not sure. I wasn't sure whether it was cars after 94 or starting in the 94 model year.
All the stickers have written on them (in very faded marker) is a date on each, the number 225 on both, and on one i can read what appears to be the name of a shop or mechanic. Starts with S and ends with k.
found this
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What AC refrigerant 'freon' 'R134a' is required in 1994 through 2007 Ford Explorer?
A 1994 and later Ford Explorer will have a factory, refrigerant (R134a) 134a system. In mid 1992 all vehicles produced for delivery in the United States were required under Federal law to have this type of system. Occassionally, but rarely, one will find a late 1992 or early 1993 system that still has refrigerant (R12) 12 fittings. But this is the exception rather than the rule and it is unheard of (virtually) for anything later than 1993 to have anything other than an R134a ayatem. Of course, it is easy to determine which system your Explorer has by checking the service fittings (the place where refrigerant service manifold guages hook up). Although as of last count there were over seventy (that's right!) different refrigerants on the market (all requiring [technically by law] their own exclusively distinct service fittings) there are only two refrigerants that (a) have ever been used by ALL (U.S.) automobile manufacturers and (b) have ever been approved by BOTH the EPA and all (U.S.) automobile manufacturers (concurrently). These are R12 and R134a. If the service fittings on your vehicle are 1/4 inch, male flare fittings, you have an R12 system. If the fittings on your vehicle have no threads and resemble the type of fitting used on modern day air compressor (an air 'chuck' type fitting) then you have an R134a fitting. If you have 'air chuck' type fittings attached over 1/4 inch male flare fittings, you have a system that has been converted from R12 to R134a (keep in mind that the specially designated fittings for some alternative refrigerants bear similar resemblance to R134a fittings, but R134a guages will not attach to them)."
You might have one of those alternative refrigerants, or an R134 conversion.