I have a M70 with hinged floorplate, release in trigger guard and integral magazine box. I think it is likely Sunny Hill mfg. Did anyone else offer the integral magazine box in custom bottom metal? It was probably mfg in the 1990's or early 2000's.

I think maybe Wisner or Blackburn

Pete Grisel was the fist that I know of to make the integral box...Sunny Hill now makes the line. Never saw a Blackburn integral, quite possible Jim Wisner made some.

Open the floor plate and pull the magazine spring out of the mortise.

Look in that shallow mortise for any stamping or machine engraving.
If nothing there either an early Blackburn or Grisel.
Later Blackburns were engraved as to model #

I allways hand stamped the model of the guard and assy # in that mortise.
I also stamped the backside of the magazine box with the assy #

J Wisner

Thanks all. No markings. Given the age of the rifle and that Sunny HIll began producing the Grisel in 1989, the shape of the guard and the integral mag box, I suspect I am correct in my assumption that it is Sunny Hill.