NOS Grace F9E question


A friend of mine gave me a Grace F9E to try on my 1200G.  He thinks it may be a good fit.  It appears to be brand new and never used.  It has a plastic protector that covers practically the entire cartridge.  I cannot get it off as it is on there very tight.  Is there any special way to get it of and not damage the cartridge?

Any suggestions would be appreciated.
tzh21y
I'm pretty sure it slides off and on.  It has grooves on the side that IIRC, align with something on the cartridge body.

Pull it straight off, but try not to put a lot of force on the sides, (don't squeeze it very hard).  Should slide right off.
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