Both of these scales are not true scales for scale modellers, they are migrated scales from hobbies that use different naming systems for scales, and are thus transposed scales for compatibility purposes in scale modelling.
1:93 as a model scale does not technically exist. It is the ratio scale attributed to the increasingly popular 20mm wargaming scale.
1:87 on the other hand, is the ratio scale attributed to HO-gauge railway models, although it is rarely stated as the ratio, and is almost exclusively sold as HO-gauge or HO-scale.
It is possible that there are manufacturers producing models in close size proximity to these scales and using an even numbered ratio (e.g. 1:88 or 1:92, possibly even 1:90 as a bridging ratio), though I have not heard of any.
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