You have hit on a very interesting feature of a single units unique feature this to the best of my knowledge was only used in Russia by 502 around late 42 early 43 pictures of this modification are very rare and not the best quality some it’s very hard to see, information is scarce on what it was for and why this was done have a look under the 502 section on the “Tigers in Focus” forum for a few pictures, this is not covered in the Jentz and Doyle books