I would check the castings for MLB serials. I've seen a few made up from recastings and usually show poor definition on things like the Bell Motif
.…. Woodwork for 'oles
.…. Back door?
.…. Lock & key?
….. Is the mech sound and working?
…… Investigate the reels, are they tin, paper or plastic?
….. Is the Jack pot bank there? If so does it trip?
.... Does the coin mech behind the bullseye glass hold the coin just played?
How bad is that handle? Re-chroming should be allowed for.
As for value, probably twice as much as double the length of a piece of string
If it's all there (as described above) and only needs a coat of looking at I personally wouldn't want to pay more than £350/£400 including all of the commissions and VAT. However I'm me and I only buy if it's a bargain. I've had a couple of these and wouldn't want another one, they're hardly pulse racing to play. If I wanted a perfect example and was prepared to pay the highest retail price then I could buy one today.
A massive issue for me these days is commission bidding, telephone bidding and internet bidding at live auctions. These are people whom for whatever reason can't get there and are throwing money at something they haven't seen. So many of them must be disappointed when it's delivered.
ps my post crossed with Paul's and echoes it.