I found an interesting article, the "Valjoux Engine", The Valjoux 7750 Engine principally on the 7750 and 7751.
Keep in mind the Longines Master Collection Triple Date Moonphase.
The last page of the article is "Standard and Special Valjoux Caliber 7751 Versions," which contains photos of those watches (or some of them).
The Longines is a Standard 7751. But the page contains pictures of other Standard 7751s which are identical with the Longines and each with each other. (except dial color)
The other companies are: J.Chevalier; Devosa; Ph. DuBois & Fils; Jorg Schauer; SINN; Jean Marcel; Auguste Raymond; Sothis; Tempton; and Universal Geneve.
A quick look at these web sites shows some are for the European Market. The much desired Sinn 6015 St is among these watches. 1760 Pounds Sterling. 1550 Euros.
Are all these watches made by one company? Who? Perhaps they all come from China. (joke)
(Incidentally, I just got the above mentioned Longines w/leather band and 2 day shipping from S.Guven in GA, an AR, for $2300. Can get phone #, etc. at Longines' site.)