in my time with auto parts, the stores had some lines that were recombined with other product lines...for example the Beck / Arnley folks coming in to renumber OE and Bosch parts with B / A numbers. as a result of the being re-boxed, many really old parts were given a new snappy, hip life... my story just to say that you may have received an NOS seal that had weathered on the shelf.

nice to fix something in the driveway that could have broken on the trail? look great!

1987 Raider - Roxy
1988 Mighty Max 2.6L Turbo - Pearl
1997 Mountaineer V8 - Freddy
2000 Excursion V10 - Freya