Looks to me like you have 3 different buggy dash's and a piece of trace chain. Unless it's a doll bed why would a head board be only 17 or 18 inches. Also a darn tiny gate. There were lots of different styles of buggies and carriages, some fancy and expensive, others inexpensive, hence lots of different styles and types of dash boards. What looks to me like trace chain has a swivel in it, it it is trace chain, then the original chain to the left of the swivel had about 9 links and a ring. To the right was more links and a stirrup like fitting to fit to the leather tugs or traces. If the chain is from army harness, then it's possible it might have a US cast into it. I have one that has that.
The dash is shown on a carriage with leather covering the frame. They bolt at the bottom just like what you have found.