NitroX, your grandfather's .22 is a rare Mauser model Mm 410 Light Sporter, made about 1925 – 1930. Distinguishable from the Mm 420 Target/Sporter by the lighter and shorter 60 cm barrel and the front sling swivel soldered on the barrel. See Jon Speed's "Mauser Smallbores" book, page 19.

The enigmatic number 459 is found on all Mauser, Oberndorf .22 barrels up to 1945. Even Jon did not know the meaning until we found it in the German 1895 proof table: It was the gauge number for .22 barrels. These gauge numbers went out of proofhouse use on rifles in 1912. For reasons unknown the Mauser factory continued to mark them on their rifle barrels, besides the mm designations. See Jon Speed's "Mauser Archive" book, page 213.