Steve. To be perfectly honest with you, I haven't a clue. However, on page 11 of R.L. Wilson's book, WINCHESTER, AN AMERICAN LEGEND, there is a picture of four Henry rifles. The description of the photo is as follows, and is probably the answer to your question.

"From the top, henry rifle serial number 11 (brass frame) with variant factory scroll engraving. NOTE EARLY-STYLE LEVER, WITHOUT LOCKING LATCH,A FEATURE ALSO EVIDENT ON THE IRON FRAME HENRY NUMBER 73." (Emphasis is mine)
My guess is that the iron framed Henry's were part of the early models before they found the need to use that lever latch. Seems reasonable to me.
Paul B.

Sounds good again Paul, I guess I don't have enough Gun books. Now if I can only convince the Wife of that. Thanks.

Steve E.......