I found this funky Rocksteady variant at my favorite thrift store last weekend. He's known as 'Dimwit Doughboy Rocksteady' and was released in 1992 as part of the TMNT Mutant Military 2 sub-theme.
I'm not sure why they went the extra mile and gave Rocksteady so much arm articulation. I am also unsure why Playmates made Rocksteady into a WWI soldier, but I suppose it was a better move than making a Nazi Bebop.
This version of Rocksteady is pretty cartoonish and ridiculous, but all of that adds to his charm. You can really tell the TMNT toyline was scraping the bottom of the barrel with this one.