Yes. Switch the capsule to its omnidirectional setting, connect the microphone to a recorder, put on a pair of headphones, hold the microphone in front of your mouth and speak toward it in a steady voice. Slowly turn the microphone around so that you can hear the response from all angles around its circumference. There will be more of the very highest frequencies right in front of the microphone, and that may be audible to you--if so, that's normal for a pressure transducer of this size.
But when you get to the 90° and 270° points, there should not be a drop in the overall response (which would be characteristic of a figure-8 microphone). If you find that there is, then the microphone should be checked out at the factory. Basically, the symptom of the gaskets needing replacement is that the capsule tends toward becoming a figure-8 regardless of the actual pattern setting.
This is primarily a concern for capsules manufactured before about 1988-1990 (sorry, I don't know the exact year). Any three-pattern capsule (or CMTS stereo microphone) older than that, if it hasn't been serviced at the factory since then, will very likely have this type of problem by now or be headed in that direction. It doesn't matter whether the microphone was in use or not.
--best regards