I did contact that company and got the following reply:
We do not possess drawing A10087 online in our database.
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This looks like it’s an RE8 oil tank with the filler on the other side.
Not a FE2B or D oil tank.
Also Drawing no A10088 are RE8 oil tank parts as per the parts manual.
(snipped)
So, they appear to be uncertain exactly which model it is for.
Any other suggestions or comments?