Cartridge identification

I have a cartridge that I need help identifying. It is headstamped D.M.K. It is a long slender rimless brass cartridge with a nickel bullet. The dimensions are: bullet diameter: .255 inches (6.47 mm). Base and rim .424 inches. Case length is 2.754 inches. The neck diameter is .280. The shoulder diameter is .338 inches. The over all cartridge length is 3.368 inches. Any help would be appreciated. Thanks.

Sounds like a 6.5x70 Ohlhoff, sometimes referred to as a 6.5x70 Spencer.

My database notes are as follows:

DWM case #483 was listed as “Kal. 6,5mm A.Ohlhoff, Portland, Ore” and no dimensions or case drawing were shown in the DWM case book. However, it has been identified as being the title for this 6.5x70 cartridge with “D.M * K *” hs (ref Buttweiler).

This rare experimental cartridge was manufactured by DWM for Ohlhoff of Portland Oregon (USA). This case was designed as a rimless .25 calibre version of the 22 Krag M95 Experimental for an experimental George.N. Spencer magazine rifle. However the two Spencer rifles in question (in Oregon - see image of display) are not actually chambered for any cartridge at all. Both rifles have wooden mock barrels. There is only the assumption that they are supposed to be chambered for this cartridge because several rounds along with a few other items accompanied the rifles when they were given to the museum.

A. Ohlhoff was evidently a CIvil Engineer of Portland rather than in the hardware/ firearms business. It appears that he acted as an agent for the manufacture of the cartridges. As he could not find any U.S. manufacturer for this round, he therefore turned to DM-K/DWM for manufacture.

Evidently, George Spencer had a small firearms workshop in Portland, Oregon. He specialised in the development of HV cartidges from around 1895 to at least 1902 including rimless 6.5mm and 5.6mm versions of .22 Krag M95 Experimental, which were made in very small quantities by DWM. This calibre may have been intended for US Military trials (as c1896 was DWM #425 6mm USN rimmed, #425A 6mm USN rimless, #425E 6mm USN and possibly the 6x56 American Luger - see M10).

The date of production is confusing. DWM case #483 is c1902 but all known specimens have the DM-K hs "DM * K * " which is generally <1897. This hs has been used by DWM after its formation in 1896 particularly if earlier DM-K cases were used. If this was the case here, then which cases were used is not known.