What on Earth does "Balkan" mean? That's too non-descript to be used in conjunction with "collection". Is it Romanian, Serbian, Bulgarian, Albanian, Montenegrin, Greek or Turkish? These countries used the three-line rifle in different periods and acquired them under different circumstances.
For example, Bulgaria bought 50,000 obr. 1891 just before the Balkan War of 1912 and these rifles looked like the one on the picture below. During WWI tens of thousands more obr. 1891 were captured by the Bulgarian troops from the Romanians, Russians and Serbians, but they had the 1910 update.