looking for ID glass insulator embossed 'M'

[steelheadwill]

hi all came across this insulator only markings I can see are the embossed m and the mismatched 21, 12 or letters on the crown.
Looks similar to a 1:04 but the wire
groove is significantly lower on this,
Any help is appreciated, thanks, Herbie

 

[epackage]

That's a B for Brookfield not an M, it's a CD 145 IMHO...

 

[2screwed]

epackage is right about the B for Brookfield. I think the 21 on the top is the mold number.

 

[steelheadwill]

Thanks all believe we have the proper ID see that many examples vary from the photos shown for identification I love how the mold number is upside down backwards whatever it is kind of like an error coin good day and happy hunting all