Pictures would be helpful, but from what I can understand I assume you mean on the right side of the frame on the trigger guard there is a HV36 marking. HV means HeeresVerwaltung and is the Austrian Inter-War Military stamp used on repairs/reworks. This would also fit to a 1919 dating slide, most possibly leftover parts that either directly went to the Austrian Army or were first given as war reparation to Czech Republic and then purchased back by Austrian firearms dealers and then sold to the Austrian Army in the 1920s.
HV36 indicates it was repaired in 1936. This stamp was overstamp of the original firing proof in that area, maybe you can make out a Wn19 under it.
Is the slide also "08" marked and the pistol in 9x19mm caliber, or is it still in 9mm Steyr caliber?