There never was a military ".38-200" round
There never was a military ".38-200" round. That designation was a Kynock one for their commercial version of the 200gr lead bulleted "Cartridge, S.A. Ball, Revolver, .380-in Mk I". The Mk I was made obsolescent in 1937 when the Mk II round of the same name was introduced with a 178 gr cupro-nickel jacketed bullet.