Hi, some mags from my collection:
It is thicker...it's an experimental 50rd magazine. A few different experimental 50rd and 60rd magazines were produced and this one nor the plum variation went to serial production. The only one approved for serial production is the 60rd polyamide, GRAU 6Л31. Similar military 50rd polyamide mags have been used in combat operations by Russian Special Forces but have yet to be approved for serial production (as far as I know). Additionally, if you go back earlier, experimental 50rd dual slabs and also 50rd and 75rd steel ribbed dual stacks were developed by a few different designers, to include the Kalashnikov team, but none of those designs went to serial production.The bake mag in the rifle above the svd looks much thicker than normal?