Topic: Curious piece of glass.

[fontanazul]

Curious piece of glass. 
At first glance I thought it would be a desktop object.
But studying their curious details: I have concluded that it is
a piece of glass for industrial use, such as peephole to steam. Borosilicate glass resistant to high temperatures Klinger factory in Austria (perhaps for export to Eastern countries).
Curious piece !! (you'll end up on my desk)

[chopin-liszt]

It looks like a wedge for holding a door open.

But that would be a strange thing to have made from glass - it would be very prone to damage through normal use.

[rosieposie]

This link may answer your question fontanazul,

http://gaugeglass.dynaflex.asia/gauge-glasses/flat-gauge-glasses/reflex-gauge-glasses/klinger-reflex-gauge-glasses

A bit more here:

https://www.google.co.uk/search?q=klinger+glass&biw=1262&bih=796&tbm=isch&imgil=gd9OJD8b6Z8YfM%253A%253BFZ57Gn1BQ7FRdM%253Bhttp%25253A%25252F%25252Fdzmz.en.alibaba.com%25252Fproduct%25252F405380333-200292812%25252Fgauge_glass_klinger.html&source=iu&pf=m&fir=gd9OJD8b6Z8YfM%253A%252CFZ57Gn1BQ7FRdM%252C_&usg=__FsfiFTBzYIzAFH90SFOa6niL-R4%3D&ved=0CFcQyjc&ei=TNVEVMLgCuKs7AbQ34GQCw#imgdii=_

Rosie. 

[fontanazul]

Thanks Rosie.
I thought in my introduction, enunciated the solution. 
(thanks for putting accurate information).