It's a strange looking beast, made by FN, and it's still in 8mm. It's a contract rifle and IOB stands for Indische Ondernemersbond, or Federation of East Indian Entrepreneurs. The barrel is just a hair under 17 1/2 inches long, the stock was modified to this change. From what I can understand, it was used initially by Dutch plantation owners, then evolved into a Police Carbine in the East Indies. As I have found out 2 lots marked IOB were made, one lot in 1948 and the next lot in 1949, each lot consisting of 3000 rifles. Then a later lot was made/delivered without the IOB crest and were marked POLITIE, est. number of 20,000. Through time some of these weapons were converted to 7.62 Nato. So this is a pretty uncommon Mauser, based on the serial number, it's from the first batch in 1948. Also, no parts other than the bolt and receiver have a serial number, the bolt is close, but doesn't match, and it's import date is hard to say, as there is no import stamp or mark.