I have located a sorry condition LM24, but the mast is removed. The mast In situ does not appear to be correct to me. (Seems too slim, short, and maybe a procter)Q1: how can I correctly identify if it is correct? Q2: Would replacement be a problem? Boat is afloat, and has “interesting” history.
From the drawings of the LM24 I would estimate that the mast should be approximately 7.7m (25' 3") long. Perhaps an LM24 owner would be able to give you a precise figure.
The original mast would (almost certainly) have been made by John Mast (in Denmark), who still list spares for LM24s. shop.johnmast.dk/en/lm-23-24-12/ They could presumably supply a replacement, but I imagine the cost may well be prohibitive. Any other brand would also be too expensive for a small boat of that age, I imagine
Any make of mast of suitable section (width/depth) and at least as long as required for the LM24 could be adapted, if you could find one second-hand. You would have to put in a bit of work to get an appropriate mast foot, mast-crane (mast top) and gooseneck fitted, and the correct number, arrangement and alignment of fittings for the shrouds, etc.
I am intrigued by what the 'interesting' history might be.