I know someone with a similar stock, but as he has fitted his to a deactivated shotgun as a wall-hanger, so he does not need to worry about minimum overall lengths or the like...such things, are I imagine a great addition to a collection, though I'd never imagine anyone fitting one to a live firing gun...
It's a pity that such things cannot be legally used anymore...if only for the sake of being more compact to transport from A to B.
A few of the 22 rifles have similar stocks, some bolt-actions too - but the minimum lengths for those are 24": measured with any folding stocks in the folded position...with a S.1/S.2 pump action shotgun the minimum is 43" with its stock folded...unless, its a deactivated gun.
Good job you had no plans to fit the above & simply got it as a curio to check it's build quality. It may even be a worthwhile project to find a local firm that can copy the design but in a fixed version? You could further save R&D costs/time by using the stock as a prototype to test some possible modifications to make it permanantly non-folding. I think you should look into it...I know of one potential customer already