Going with no guard was a good choice. In the 18th c., guards on any knife other than a double edged dagger, or repurposed/broken sword knife, would be rare to non-existent. One of my books on early knives has one very much like yours, and it was an early to mid 19th c. knife. You did well, especially considering what you had to work with. And as I recall, a very similar knife was found near fort Ticonderoga. It is considered an 18th c. knife, but has poor provenance as far as exact location of being found, and when.