50-500 USD
Find a gunsmith and ask for help
50-200 USD or so
$15 to $40 depending on condition.
Gun shows, e-gunparts.com, want ads.
Could be worth up to $500 for an immaculate, all matching rifle. It replace the Mauser Model 1871, used a 7.65x53 round nosed cartridge, variants of the rifle were also adopted by Turkey and throughout most of South America.
Depends on condition and originality. Anywhere from $100 to $275
$275-$450, depending on EXACT model and EXACT condition.
5-50 usd
It may not even fit an 1891 Mauser. Bolts are not a "drop in" part- they may require fitting (headspacing) to that individual rifle. That is where a gunsmith earns his pay.
7.65x53, also known as the 7.65 Argentine or Belgian.
They made those from 1890 to the early 1900's
10-1000 USD or more depending on specifics