Inside is, as advertised, a small clockwork motor for powering Meccano models. These 'Magic Motors' are fairly common online, but usually just the motor & key are offered. This one came in the box complete with all its accessories.
Still (or again) attached the inspection label and the key in its small paper envelope. A small time capsule almost, this might even be from unused stock. If not, it was always very carefully looked after and kept complete. Guarantee slip stamped for 1952.
The great thing is that it comes with the half-inch pulley. This you really want to have, to be able to drive models built from a standard Outfit. Also the full set of six drive bands were in the box. Three pairs of different lengths, still rubbery and very usable.
Carefully stored the ephemera and then instructions given to the crowd on how to wind it with care according to the arrow on the motor; it works! Excitement all round, so out with the Outfit number 3 and see what can be made. After some tinkering (and failing) with putting it on wheels, a much easier model is a pneumatic road drill. (Hadn't thought of that.)
This does work and is surprisingly and satisfyingly noisy!
It may well be that the spring by now is too old to drive a small car, but a simple windmill should be manageable. With a set of special Windmill Sail parts (number 61), a little windmill is made. Maybe not the most ergonomic spot for the motor control though...
Moving the motor lever; it does work and whirrs the metal sails round at a good clip (sharp edges and all).
The little motor does fascinate them. No batteries, lasts forever! Even though the youngest is getting much more adept at the little screws and nuts, Meccano parts do require a different approach to construction than what they're used to. It is clearly not stacking bricks or just snapping parts together. Step-by-step instructions or some guidance are really needed for the 7 year old. (Except for that pneumatic drill, that was his own original idea.)
Overall the experience with this 1950-ies Meccano convinced me that actually the cover illustration of the manual is correct. Leaving aside that unrealistic, giant dragline; this is not a construction toy that can simply be given to children to play with.
It should be played with by children together with a parent close at hand!