I can say with a high degree of certainty that a normal auction house will have no idea either. Locks are a highly specialised field with a very limited market and a regular sale is not the best way to get the best price.
There is a specialist auctioneer who deals in such matters :
http://www.schofieldauction.com/
and many serious collectors take the catalogues for their sales. Whether the item is going to be the sort of item they would handle, or best listed on ebay I cannot say this particular lock being outside my area of interest / specific knowledge.
Perhaps BBE could suggest a ballpark value ?
****** Edited after posting - I checked and it’s been a while since they did a lock auction, maybe they are not in the business anymore ??? ********