Originally Posted by
bike recyclery
Couldn't quite tell, but that makes sense! In that case, does anyone know what the 21 stands for?
21 is a date code, or probably better stated a "batch" code. This was during the dark days where demand for Campagnolo fell off a cliff. Shimano 7400 was pushing Campagnolo to the side.
'86 or a bit beyond is a good period for these. Note the stamped logo on the arms, earlier version. Distributors had much on hand and unlike bread, did not have to rotate stock so vigorously.
You will also find 31 in a square, and 11 in a square.