I have a Sweetheart vintage 45 with the box; here's the detailed particulars if you want to build an exact replica; don't worry about pulling the wool over someone's eyes, the decals are very hard to come by:
Stock is 5/16 thick, finger jointed construction.
Exterior dimensions: 12 3/8 x 7 1/2
Bottom section overall is 3 3/4" deep, with bottom nailed on; just the finger jointed portion is 3 7/16" without counting the bottom
Top is 1 5/8 with the top glued on (I couldn't find any brads); just the finger jointed portion is 1 5/16 without the top.
Inside the bottom there is an angled bar nailed to the bottom, 1" high x 3/4 wide, with two holes on the left, the first 11/16 on center from the right side, the second 1 13/16 on center. I couldn't get the precise angle of the bar, but its bottom left end is 2 1/8" from the front left inside corner, the top right is 2" from the upper right inside corner.
the iron storage is on the right, with two slots for 1/8" stock; two 1/8 dados , the first 3/16ths from the inside edge, the second 3/16ths from the left edge of the first dado. These dados are in both the top and bottom.
In the top is a stop block to keep the irons in tight when the lid is closed, it is glued into the right side of the top, 9/16 wide and 13/16 tall.
Here's some pics to give you some orientation, and to show the hardware: