If it came with the aluminium tube, I'd say its a DVH (version about 3), probably the first version sold by Dday, but essentially still the DVH molds. Derek will no doubt correct me. Check out my build in my signature below, basically the same parts you have.
I just used epoxy and locating 'pins' to secure my real folding stock. No idea about aluminium brazing, sorry.
Good luck. Will be watching...