Nineteenth Century Clasp

I’m working on recreating an interesting nineteenth century diary/wallet from a few photos and would love feedback or direction on how to keep it closed.

It has a diary at center with wallet on the left and pockets to the right for miscellaneous items like postage and tickets. There’s a small bit of brass visible under a leather tab on the right side. A photo of the back shows what looks like light abrasion marks where the closure should (at least in theory) be, but a full zoom reveals nothing (the photo I’ve included here has been greatly reduced).

I can’t think of why the brass bit or leather tab exists unless there was a way to secure the wallet shut, and wonder if you’ve seen anything similar. I’ve guessed at that brass bit being a hook and have fiddled with both a brass bar for it to catch on (pictured) and a brass slotted plate to handle more or less items in the gusseted wallet. Any ideas on how this might have originally closed?

Original showing leather tab and small piece of brass

The original laying open. Leather tab on left and what looks like a small abrasion where a closure may have come detached from the right panel.

Layout of inner portion.

Our prototype for checking function and fit. The brass rectangle to the left is a thin bar for the hook to catch on.

Closed with hook secured.

Sample hook and slotted tab instead of the bar, giving room to adjust for pre and post payday wallet thickness.

Replica of a nineteenth century hook/slot closure for clothing. Made of copper. (From Goose Bay Workshops.