Prior to Tamiya coming into the American market in the late 60s, armor was generally 1/40 (an odd size) for Revell and Adams, and I believe Renwal's kits were 1/32 or something close to that. Tamiya made such an impact on the market that it became the defecto armor scale. Regarding ships, sailing and craftsman wood models were the various fractional sizes (1/48, 1/96, 1/192). Then came along Tamiya again with their big ships in the 70s at 1:350 which set that scale. The other model ship scale is 1:700 which is 1/2 1:350. Prior to Tamiya picking an actual scale, all the other plastic ship kits were "Box scale". Revell, Monogram, Aurora all had standard size boxes they used for model ships and the models were sized to fit those boxes. Model planes had the same problem. Monogram's planes favored 1:48 and did so faithfully, but Revell was all over the place. You didn't find the actual scale listed on any of those first generation plastic model companies' products.