Totally agree with everything that Muskett says, I would dearly love to own one but it would likely be one that I wasn't afraid to get out and shoot with.
I would go one further and state that the Centenary is the best looking air rifle I have ever seen but that's just my opinion as I am an Airsporter nut, I only have Airsporters now, they are my love especially my MK1 and MK2 and my S carbine, the latter of which would be impossible to value because I would never be prepared to sell it!
Yes I agree with Muscett again, he is totally right, some rifles are worth a lot more to their owner!

One thing that a prospective owner should consider, Having paid that £700+ for the 'mint' and unused Centenary, bear in mind, the lubricants used in it's construction all those years ago (25+) will have deteriorated the piston washer etc, at the least, you will record very low power on a chrono, the rifle will probably need a full strip, clean up of all old lubricants and a relube and rebuild.
Who would you entrust that to? I would only trust myself to do it, some would have the additional cost of returning it to the BSA factory or a gunshop etc!

Airsporterman.