I was wondering where that was from. As far as I've heard, the German military did not capture any Mark V tanks, or at least didn't get any into their service. Or is that wrong?

I don't think anyone knows why that tank was painted with German markings. The tank itself was captured by Red Army during the Civil War, and not too long time ago was repainted in the colors it used to have. Back then in Soviet Russia Mk V were called "Ricardo Tank" due to the name of the engine.