Thanks for the replies. Pretty sure is not an old sprinkler head. Given the location where I found it (have found many things dating from the late 1800s to mid 1900s) I would have to go with a decorative heater/floor plate or crawl space/foundation vent cover. Will wait and see if any other replies come in before declaring solved. Thanks again to all.
Where I found it along the creek here in town is now overgrown but during the Victorian age there was a chicken farm there as well as a shoemaker.. Before that it was part of the estate of one of our town's founders. So your thinking it may be part of a fancy grave fence may very well be true? Thanks for your reply.