The AK-47 rifle was formally adopted in 1947, as the name implies, and went into production in 1948. In this very first form, it used a stamped receiver with front and rear trunnions riveted in place. Unfortunately, while the hand-fitted preproduction guns were quite excellent, the manufacturing processes and quality control left a lot to be desired. The stamped receiver was relatively thin (especially compared to previous stamped Russian small arms like the PPS-43), and was very susceptible to warping during heat treating and other parts of the manufacturing process. The guns that met QC requirements were every bit as good as expected, but the high number of rejects nullified much of the point of having those stamped parts in the first place.
For this reason, AK-47 production ended in 1951, and a milled receiver was developed to allow rifles to continue being made while the engineering and production team worked to improve the receiver design and the manufacturing processes around it.
Today the first pattern AK47 is an extremely rare weapon, and I am grateful to the private collector who allowed me to video this one for you!