The boxes are bolted on weights for trials YES. The Panther A is "partially" correct. Continue to look at the photograph and more details will appear.
You got me, I've put a lot of time into comparing with other pics of Panthers, but I don't see anything obvious. About the only other thing I see, is it appears the hull has zimmerit armor coating but the turret doesn't and I can't even be sure of that as the pic doesn't enlarge well for a closer look. Comparing your pic with others on several sites, there seems to be some doubt as to the true identity of the tank anyway. One site lists it as PantherD and another PantherA.
Yes, you are the winner. This is a picture from the Polish Army testing the Panther out in 1946/47. Thye had to create this tank from the D model hull they had and an operational turret. This was sent ot me from someone from Warsaw Poland last year. It took me a few hours to correctly identify the differences as well.
I haven't had a lot of luck picking tanks that were hard to identify, hopefully this will be a little tougher.
Just as I suspected, That one didn't take long either. You pounced on that one like a Panther. Good job and over to you.
German Panthers disguised as U.S. M10 tank destroyers during the Battle of the Bulge The Germans cleverly disguised their Panthers to look like the M10 tank destroyer. I don't know how well this worked at the time, but from a distance they appear quite similar. Check this site: Germans Disguise Panthers, Cleverly Imitate M10 Gun Carriage, WWII Tactical and Technical Trends, No. 57, April 1945 (Lone Sentry)
Messala, that would be good enough, although operation name was Greif. Slomo, they do look quite similar, although I don't know about the sound of their engines, it would be almost impossible to change. Your turn, Messala.
Try this one. An unusual looking turret. http://www.ww2f.com/members/slomo-albums-unique-tanks-picture3404-copyoftank.jpg