Peter,

It isn't LX it's 38 K under an "umbrella" or possibly 38TK. I've looked around for it but haven't found it. It does indeed look like a manufacturers logo. The "T" also resembles the government acceptance mark but doubt that is what it is with the 38 and K under it.

I don't think there is steel cast scabbing on it, that's black paint. It dos show evidence of being "ground" as there are parallel marks. I don't own a micrometer so can't help there.

The designation looks engraved but the logo looks stamped.