This is an antique, complete Milton Bradley "Springfield Industrial Drawing Kit", patented 1889. You know I love early Milton Bradley, and here a very smartly designed set including two drafting triangles, a t-square, and a drawing board. 

When hung up (from the handy hole at the end of the t-square), I think it looks quite a bit like the front of a button down, collared shirt, and, relatedly, immediately evinces wooden Shaker sweater stretchers. (And there are three purple marker dots/stains marching down the length of the t-square that make it feel as if its onetime owner might have seen the whole thing as looking like a button front shirt too!)  Best of all to my sensibilities is that on the flip face that t-square (the inward facing side when assembled as in first photo), they wrote, in cursive: "this is a tea square." And how nice and rich the idea of a "tea" rather than a "T" square, the drawing board here a tray of sorts for serving it up!

14 3/4" x 9 3/4" x 3/4", Very good antique condition. Nice warm patina to the dry wood. General wear around the edges here and there, and annotated t-square as described above!