I've got no idea what that engine is worth, but if he's going to melt it down the scrap weight of it isn't that much. You could probably get it for £50 as that's more than he's getting for it. If you really want it give him £100 and watch his eyes light up 
email (option): horror@blueyonder.co.uk
Only around 750 M24s were made, spread between 1938 and 1939 types which were different...and it's the first version of the Gold Star...
It would probably sell for £1500- £2000 without too much problem (in the UK)...
Let him name the price and give him whatever he wants...it won't be anything like that much....
....Ian
email (option): ian@wright52.plus.com
I've got some swaps if the guy is interested. one is a Stradivarius that a local logger found & is going to chop it up as firewood tomorrow if no takers & the other item is some old silly Italian bugatti car that my local farmer used to keep chickens in but he now buys & sells dynamite & is going to demonstrate to a customer on Thursday by blowing it up. 
OK but seriously, as already pointed out they were sold in 1938 & 39 but also a batch of engines were produced or supplied for a Scandinavian (I think) order after the war for competition use
Regardless of year a good barrel will fetch over £1000 & a good head will get toward £1500 so there is a good starting point on value. the barrel particularly was technically advanced both in material used & production method.
['the barrel particularly was technically advanced both in material used & production method.']...
Unfortunately the rocker box was weak and easily damaged...An acquaintance of mine has recently had some new ones made..and also some barrels...Ian
email (option): ian@wright52.plus.com
Unfortunately I know of two totally true stories along similar lines. Thanks again for the guidance.
Unfortunately the rocker box was weak and easily damaged...An acquaintance of mine has recently had some new ones made..and also some barrels...Ian
[/quote]I saw the 38 type barrels on Georges site they look nice.
The rocker boxes i dont think is a design fault. people in the past undid them with the valves compressed & if you don't release the left side bolts first the box twists up from the spring force & snaps at the left side lugs, its just bodged removal, there's no real stress in those areas once assembled.
No problem at all if a bit of common sense is used by slackening the tappets ETC
Lots of the VTwin rocker boxes have been weld repaired for the same reason ie undo the right side bolts with the valve compressed & the left rocker box lugs woukd easily snap.
I was lucky in that my barrel was on standard bore & perfect condition. but the article I read a few years back spoke of a production method used in the aircraft industry where the liners were fused in by being spun at high speed or before the barrel metal had cooled. It was something to do with maximising liner contact with barrel which can't be achieved by casting the barrel onto the liner or something like that.