The Silenced Pistol is a gun just like the Deagle but with less range and more fire rate. It is effectively a reskin of the Skeleton Gun in terms of stats besides the fact that it weighs slightly more.
It isn’t actually silent, it’s likely just a game reference or it’s an expression (it silences your enemies?).
This gun is best for smaller maps such as Nuketown because of its high fire rate and good range.
The weapon is a reference to the Hitman series. It resembles 47's signature Silverballers.
The description is a reference to an item in Hitman: Blood Money where one item says, "Allen, please add details".