NOS Shure V15 type III cartridge opinions


I know this sounds crazy but going thru boxes stored in closet for the past 40 years and found one of these I had purchased in 78 as a spare and never used. My question is should I open it up and give it a spin on my vintage TT or keep it to replace my in use cartridge until it goes south or open it install to see what happens? Wished I had another headshell. I read this was the best mm cartridge build, great all around sound and unsurpassed tracking. 
Or put on market? I'm leaning toward trying it out but then again?
128x128gillatgh
Use it!  The VI iii is an excellent cartridge. My Son has one and uses it daily. Wonderful dynamic and well balanced. 

N. 
Thank for the input. Consensus seems to be that the suspension for the stylus may be suspect after all this time. I did visually inspect the cartrige and stylus with a magnifying glass and see nothing visually other than that it is pristine.  Just in case I did look for a replacement stylus and found only aftermarket stylie ranging from 13 to 88 dollars. A Phanstiel, supposedly made in switzerland, is 25 dollars and the highest priced ones are from Japan and shipped from there. Does anyone have any experience with these aftermarket stylus?
Any information would be helpful and appreciated

Aftermarket styli vary enormously in price and some are outright bad. The Japanese Jico ones have a good reputation. Shure themselves recommend their M97xE cartridge as the best replacement.
As an anecdote, I recently noticed that the audio archive of the British Library use the Shure M44 cartridge for their digitization of some old recordings, using specialty styli: https://www.youtube.com/watch?v=yI5DYJPSf-A&feature=youtu.be&t=162
The stylus is a major part of the sound character and tracking prowess of the V15. All of the aftermarket offerings will change the sound. Most are so inferior as to be ignored as an option. The only one that is consistently said to be as good or better than the OEM stylus is the Jico SAS:
https://www.jico-stylus.com/sas.php

There is debate as to the superiority of that one as well. Try your original. It may play fine. Listen for excessive sibilance and other signs of mistracking and go from there.

Dave