What kind of lamp is this?

[Lampje]

Hello,
I have a question about this lamp.
Can someone tell me when it is manufactured?
It has some marks on the inside. 

5 A0
  85

865

And some marks on the outside of the shape. ETL No. 1444 (Could be etched)

The construction inside looks like a sintered tungsten filament to me, but the lamp is missing the pip.
So I don't know what kind of lamp I have.
It has a tinned cap,  Edison E27(E26) base.

[Tim]

Sorry, I can't be of much help with this one.  I agree, the way in which the filament is fastened does look similar to the construction of early sintered tungsten lamps, but the lamp is tipless - a "feature" most commonly found in later lamps.  It's a puzzler for sure.  Maybe someone else will recognize it.  Thanks for sharing the photo nonetheless!

[Lampje]

Hello,

I got the answer on the lighting gallery.
It is a photometric sub-standard lamp used for calibrating optical measurement equipment. Ca.1930