There are many things to consider on old shotguns and this is especially true of Lefever Arms guns. Most Lefever are OLD, yours was made in 1906 or 1907, which puts many of them truly in the antique category. If the gun is lose and rattles when you shake it and has little or none of its original finish it's probably just a wall hanger with a value of no more than a couple hundred bucks. In good or better condition though, and condition, originality (unmodified in any way), and grade are everything, the value can range from $500 to over $20,000. Your best bet is to go to one of the major book stores and get a copy of one of the firearme pricing guides, similar the Kelly Blue Book for auto's, and evaluate the gun yourself.
Made in 1904. Value depends on grade and condition.
The Lefever was mfg. in 1935.
If it is a double, remove barrel and you will see it along with serial #.
around $6000
1927
Requires professional appraisal.
Turn of the century.
The best that I can do is say that the Lefever Nitro special was made from 1921-1948.
Blue Book of Gun Values
To get a parts breakdown you would need to take the shotgun into a gun store. The store will be able to provide an estimate, or order new parts.
Lefever made several models through three different versions of the company. Not enough information.
The shotguns were manufactured by Ithaca from 1921 through 1947. Yours was manufactured in 1928.