The 10.3mm Clark was based on the .500 Express (12.7mm) case and was submitted to the Austrian Military Trials of 1887 by American designer, Henry F. Clark, for which he was awarded US and UK patents in 1885 and 1886. The idea was to seal the bullet in the case with the crimp partially covering the bullet (see 10mm Clark loaded specimen) but the idea failed and was abandoned. This was the brass case but there was also a bronzed case version (GR#221). See also Motz, Vol.1 p. 86 and Motz& Kohlmann Vol.3 p.118 and 287. (Roth #222).
