As said they are both Russianicon Capture, hence all the mixing up of numbers, overstamping and the 'X' crossed rifles USSR mark. The overstamping of the Mod 98 on the side of the reciever of the byf 44 is an oddity though, don't often see that level of electrostenciling on RC's.

Generally all you can usefully date it the original receiver now, as shown on the top each one, the rest of the bits can be from any date and maker between 1935 and 1945...which can be worked out from looking up all the Waffenampt stampings, but you'd need the books and taking everything apart to go over with a magnifing glass etc.

So,
The one marked on the top with S/147 1936 started out being made in 1936 by JP Sauer & Sohn, Suhl. Can't seem to see a photo of the serial number, which may have been removed?
The one marked on top as byf 44, started out being made by Mauser at their Oberndorf-am-Necker factory in 1944. At least this has a visible serial number.