If this rifle was included with, (or in advance of) a Military rifle order/purchase, would you have a guess as to what country and what year?
The only clues we have for the rifle's original destination are: A country supplied by DWM before 1912 with M98 action military rifles in 7x57. Unfortunately there are several possibilities:
Mexico, several models, both rifles, carbines and short rifles from 1902 on.
Brazil, models 1907 and 1908, both rifles and carbines.
Colombia, model 1904.
El Salvador, model 1904
Uruguay, 1908
Make your choice. My nod goes to Mexico, as the rifle apparently was in the USA before WW2, when the Lyman sight was installed.
Do you think that DWM built this double-set trigger arrangement, or did it come from another source such as Oberndorf? Do you think the "small-circle" inspection marks (see pic) found on the triggerguard/floorplate, bolt handle, follower, etc., etc., would indicate that at least the assembly was all at the same time and location?
Maybe the smaller set trigger parts were bought in by DWM from their subsidiary Mauser, but Mauser did not make separate set trigger housings. Mauser set triggers were always mounted directly into the accordingly machined triggerguards. I don't know about the meaning of the circle stamps right now, but the like serial numbers on all parts are proof enough that the rifle was assembled from rough parts at one time and in one place.
Were either of these rifle contracts offered in 7mm cal. to give us a clue about this rifles origin?
Though a small number of Vegueiros in 7x57 were sold to a Brazilian police force, this is no clue to the rifle's original destination. The Vegueiro is not a Mauser action, but was developed from the M88 and Mannlicher turnbolt designs. Only the bottom metal is interchangeable with true Mausers. For these "promotion" rifles DWM often used left over parts from military production runs, as did Mauser for their C-type rifles. FI all the 3 "Plezier" Mausers I have seen, that were shipped to the South African Boer Republics together with military M95 (round bolt face) rifles were built on M93 (square bolt face) actions left over from Spanish orders.