I doubt this is an experimental rifle, as far as I am aware these types of triggers are for hunting purposes, turning down a bolt is common enough for that purpose also, though it looks like the bolt is mismatched anyway (so irrelevant to any former status).
Besides the obvious, that double triggers would serve no purpose for a military application, you would need good pictures to offer much of an opinion, - like the date of the rifle, because although experimental rifles can be found after introduction of a variation, they seem to be more common at the beginning (pre-production). Also Erfurt is hardly known for trials rifles, usually they are the patent holders (Mauser/DWM) or Spandau business.
Anyway, these are just some random thoughts and I doubt many could answer your question, not too many specialize on this variation and now that CB is gone, I wouldn't even know where to suggest you begin your journey studying the rifle. You might buy Storz book on the M71 & M71/84, the strength of his books are in museum collections and archival work, it might be the best place to start, but I doubt it will answer your questions. This subject reminds me of Richard Law's boondoggle in Backboner II where double set triggers were applied to a bcd/4 "sniper", which garnered a considerable amount of ridicule two decades ago... odds are excellent this is some bastardization being passed off as desirable.
