They go for what people are prepared to pay,if you have an ebay account you can do a completed item check.This may go for 500 or a lot more who knows.Admin can write a letter to say you are a member of this forum,any other classic magazine subscription or clubs will help, agreed value usually photo's.If I was bidding I might go to 700 with out seeing it,but I have a partner who can weld,best get some one to go & view it if you can who knows a thing or two.
Sybhil & no1