Originally Posted by
dddd
The Skitter derailer is pretty rare.
And might give some clue, at least - pre-1970 examples are marked "Maeda Iron Works" on the rear parallelogram plate, post-1970 stamped "Maeda Industries, Ltd.", according to <http://www.disraeligears.co.uk>. The 2-letter date code for Suntour stuff started sometime in the 1970s, not sure when exactly...