Those old 3TTT Record stems use a 7mm Allen key for the expander bolt. To the best of my knowledge they only came in 22.2mm. Certainly, the old catalogs do not provide any options other than extension length. There's very little clearance between a steerer tube and stem, nominally about 0.025mm (0.001"). A metric steerer tube is 0.2mm (0.008") smaller than a an imperial steer tube so a 22.2mm stem will be an interference fit but the difference is small enough that it can probably be forced. The other possibility is that the metric steerer was reamed to take a 22.2mm stem. The first step is to obtain a 7mm Allen key and see if the stem removes normally.