Can anyone ID this empty shell casing? The only stamp I see on it is in the pic.  Approx 11 1/2 inches high.

Could this be a WWI US 75mm?

You need to get more accurate measurements. Get the O.D. under the driving band ( looks like 75mm?) and length from base to top where the fuze screws into. Is the small hole at the top threaded?

11 hours ago, 27Division18 said:

Could this be a WWI US 75mm?

More than likely it is a 75mm....The base tapering down to 2.5 inches is equivalent to 63.5 mm (25.4mm = 1")....As stated, take a vernier caliper and measure the diameter of the drive band....Should measure under 3" (2.9527") which would be 76.2mm....Bodes

I think it's a WWII round vs WWI. 

The single low pressure driving band indicates WW1 technology. By WW2, notice all driving bands were wider, and had up to three raised bands to seal the higher pressures. Howitzers still had a single band due to the lower pressures.The earlier Sherman tank round is an exception, it still used the WW1 era case.

 

The later 3” ( 76mm) gun ( G, not H) and Navy 3”/50 had three sealing rings incorporated into one wider driving band.