100 or so
.32 caliber. In a semi auto handgun, probably .32 ACP
http://stevespages.com/ipb-remington-51.html
Value is too difficult to be accurate without seeing the gun. Condition which includes the amount of original finish and original configuration will determine value. Recommend taking it to a gun shop for appraisal.
50-300 depending on speicifics
Used good condition $200.00
value depends on overall condition and caliber............
Model 51 manual located here - http://stevespages.com/pdf/remington_51.pdf
150-300 USD or so
Which .45 handgun are you referring to? The .45 Colt revolver (Peacemaker) goes back to about 1873. The traditional "45 Auto" was adopted by the US Military in 1911, but there were other, earlier .45 caliber automatics. And of course, .45 caliber black powder ball and cap pistols, ball and cap revolvers, etc are MUCH earlier than the Peacemaker. So... which handgun?
100-800
About $100-$125