Before WW1, the Mauser patents were still valid. Anyone wanting to build a M98 action rifle had to buy a commercial action from Mauser. The only other makers of M98 actions at that time were DWM, who made only military rifles for export, and the German state arsenals. So you had to either buy a new, complete military rifle by DWM and sporterize it or buy in an action or barreled action from Mauser. Those commercial actions by Mauser sold to other gunmakers can most often only be identified by the Mauser serial number stamped under the receiver ring and on the rear wall of the magazine box, invisible on the assembled rifle. If you care to go through Jon Speed's books carefully, you will notice Mauser up to 1914 sold about two thirds of their commercial production as actions only or barreled actions to other gunmakers like Sauer &Sohn, Haenel, Rigby, Holland & Holland and you name them, most of them through wholesalers and export/import houses. Only the aftermath of WW1 with hundredthousands of ex-military rifles on the world market changed all this.
So most of the pre-WW1 Suhl made rifles marked by other retailers are indeed assembled on Original Mauser actions. There was no such thing as a "guild gun" in Germany! The "Guild gun" is an invention of American collectors who did not understand how the European guntrade worked.