Mystery ordnance object ID needed.

[HoldThePickle24]

Hi gang, once again I’m trying to solve a mystery. A collector friend came across this thing and I’m stumped. It’s about 3.5in/89mm diameter, has a removable top which appears to have a powder train cut into it with second timers indicators.
My guess would be some sort of mortar piece, possibly part of the German “coal box” trench mortars? Any other thoughts would be appreciated. Thanks!

 

[Alpini]

it's a russian WW1 91mm mortar shell:

 

[HoldThePickle24]

it's a russian WW1 91mm mortar shell:

@Alpini I think you’ve identified everything I’ve ever posted on here. Thanks so much!! You’re a wealth of knowledge for this stuff

 

[Alpini]

I think we already had a thread about this mortar shell in BOCN several years ago but I don't try to find this thread.

The mortar is called 35 Ln (lines, one line is 1/10") which is about 37mm. Did it use a 37x94 case as propellant?