In looking at it some more, there seems to be some confusion about what the catalog number of the older tabs-on-the-outside, 1966 catalog only version of the Electro-Launch is/was. The catalog page calls it FS-4 (just like the later one) but the instruction booklet calls it FS-1, just like the prior wooden-based Electro-Launches (see 1964 and earlier catalogs). Ahh, minutiae. It makes me wonder what "FS-2" and "FS-3" were as well.....

After a bit: I found FS-3 in the 1964 catalog HERE - it's called the Astro-Launch and is essentially an earlier, clunkier (and more expensive - probably because of the actual key switch) implementation of the FS-5 Launch Control System. But still no "FS-2".

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Bernard Cawley
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