We have in the database entries for some models under both of the above as manufacturers names.
From Wikipedia.
On 27 June 1967 Dassault (at the urging of the French government) acquired 66% of Breguet Aviation. Under the merger deal Société des Avions Marcel Dassault was dissolved on 14 December 1971, with its assets vested in Breguet, to be renamed Avions Marcel Dassault-Breguet Aviation (AMD-BA).
As far as I can determine there never was a Dassault-Breguet company as such.
Many aviation websites have standardised on Dassault and in any event I have often found it to be difficult to decide which individual airframes belong to which manufacturer when company names change.
We have 8 pages of Dassault-Breguet entries and 40 pages of Dassault entries if this helps, many model names appearing in both lists.
I propose that we use only Dassault. Does anyone disagree please?
Malcolm.