Strange German concrete mine

[Tmine35]

Photographed this concrete mine in a Finnish Engineer's museum recently. They say it's of German WW2 origin. Sorry I have no dimensions but it's bigger than normal Stockmine but too small to adopt an ice mine bottle.
Known to anyone?

 

[Fuzeman]

I would have thought it was a fragmentation sleeve for the ice mine , allthough it could be a locally produced sleeve for such a bottle mine !

 

[Tmine35]

The problem is that it is approximately same size as ice mine bottle - thus no change to have a bottle cast in concrete, concrete layer would be millimeters only and it makes no sense. Further I could not see any glass part inside the top opening.