Early Generation Unfrosted Tip MN21?

[ebuchner]

Has anybody here ever seen/used an unfrosted MN21 in the wild? I was browsing an auction site and came across what appears to be an unfrosted MN21 in an M6. It's kind of a fun curiosity that I wanted to share in case anybody else wanted to oggle at it or chime in on.

 

[michaex]

Perhaps it's simply MN20? I've never had unfrosted MN21 in my hands.

 

[ebuchner]

The problem with that is that the MN20 is a tip-frosted T1.5 lamp, but that's definitely a chunkier T2.5 envelope. Maybe someone just stuck an N62 in there? That's the only T2.5 lamp they offered (that I'm aware of) that came standard with no frosting