Another nice rifle you've got there
I think everyone has beat me to the consensus on your 1958 'K' Tula refurb. I do however disagree on the fonts matching and this being the likely original matching receiver cover. The fonts are close but they were definitely not done by the same stamp. This by the way, doesn't matter to a refurbished rifle most of the time, with possible exceptions being a rare year cover (ie; 49' tula, 53' izzy) which could hurt the value if the cover is not original, but again, does not matter to a refurb stamped blank cover like the one pictured.
I've highlighted the 3 most distinguishable examples that I found that leads me to believe this;
- The cyrillic 'U' is the most apparent, with no gap present at either the fork or the tail in the letter as opposed to the very wide gaps at all intersections of the letter on the bottom example.
- The number '6', on the top example the 'hat' of the number extends past the body of the rest of the numeral whereas the bottom example stops far short.
- The '0' is struck deeply on the right/ top right side of the number on top, where the bottom example is almost the opposite. The bottom stamp is also, much much thicker of a line and to really see the difference look at the size difference of the center circles.