M.U.S.C.L.E. Hard Knockin' Rockin' Ring Wrestling Arena
The M.U.S.C.L.E. Hard Knockin' Rockin' Ring Wrestling Arena was the only playset in the American M.U.S.C.L.E. line. It was a pretty cool idea... you and a friend put your wrestlers in the ring, and duked it out Rock 'Em, Sock 'Em Robots-style until there was only one M.U.S.C.L.E. standing! Certain M.U.S.C.L.E.s performed better than others because their bodies fit the clamps differently. Unfortunately, the plastic they used for the clamps was relatively brittle, and they broke pretty easily.
As Universal Ruler Supreme discovered at Naochin's Kinnikuman site, the wrestling ring had its origins in the Japanese Kinnikuman line. There were two rings: the Pro-Wrestling Game, which seems to be the source of the MUSCLE ring's "body", and the Battle Game, which has the same joysticks and figure clamps as those of the MUSCLE ring.
The M.U.S.C.L.E. Wrestling Ring cost $9.99 in the 80s (according to scans of the 1986 Sears Wishbook at Action Figure Archive).
M.U.S.C.L.E. Wrestling Ring Boxed
The box showed a M.U.S.C.L.E. Wrestling Ring somewhat different than the production toy: the clamps are noticably different (a pity, since those on the box look more durable). The box pictures also featured a Terri-Bull figure that is different from the actual included figure. The back of the box had a colored version of the Muscleman and Terri-bull illustration (again, the Terri-bull is inaccurate to the figure included).
M.U.S.C.L.E. Wrestling Ring Loose
Taking the M.U.S.C.L.E. Wrestling Ring out of the box, you'll see that a cardboard box protects the ring while providing an area for the figures to be placed so they don't flop around in the box. Note the decal on the side of the ring (shown below) that seems to be inspired more by the Kinnikuman manga style than the M.U.S.C.L.E. toons that are normally on the American toy packaging.
M.U.S.C.L.E. Wrestling Ring Exclusive Figures
The Wrestling Ring came with two exclusive figures, Muscleman and Terri-Bull, neither of which were on the MUSCLE poster. The Muscleman is a slightly smaller version of #141 (see this comparison scan), while the Terri-Bull is a completely different figure. This Terri-Bull sculpt, however, was included in neon green with the Board Game.
