Those motors sound very like the ones I bought from Zapp around 10-11 years ago - described as Nema 24 as the case is just a little larger than '23. To reassure you, mine were used on my mk1 router and are now in use on mk2, still running just cool enough to hold (= almost but not quite too hot to hold!)

Mk1 router was MDF, built in a hurry for a special job. All the structural integrity and stability of cold-rolled cow dung. Mk2 is welded steel. I suspect that your mk1 will also lead to a much-improved mk2!