Remington's website has what you are looking for.
Manufactured 1919
Condition?
Click on the link below for photo Model 51
50-300 or so
Depends on condition, condition, and condition. From $100 to $1,200 LNIB.
Greatly dependent on condition. from $200 to $1,200 for new in the box.
The value will be determined by the condition of the pistol. Anywhere from $0 to $500. In Mint condition especially in the box they can be worth double that.
$150 or less, depending on condition.
You can only use .380 ACP ammo in a .380 pistol. Period.
The Remington Model 51 pistol was not made by Walther. Has nothing to do with Walther. See the link at the right for a reproduction manual. sales@countrygunsmith.net
Depends on original condition from a $100 parts gun to as much as a $1,200 new in the box.