This is a textbook example of a recovery that warrants a round of electrolysis.
Keep eyes on it like hawk for good measure, and with patience and persistence you'll be able to eventually slide that cartridge right out and possibly have another angle of approach for information/dating purposes.
Don't run current directly thru the cartidge however... it -will- disentegrate!
When it's all said and done, seal it for preservation!
~Tejaas~