What is the age of Lefever Nitro shotgun 358044?

The Nitro Special was introduced in 1921 and discontinued in 1947. Yours is fairly late, probably late 1930's.

Answer

Ithaca Firearms manufactured the Lefever Nitro Special (A Grade) with serial numbers between 357300 and 361199 in 1947. This was the last year that model was made.