Hi Susan sounds like an interesting bracelet and a great investment! The upside down tear drop shape could be the maker's mark, or a country mark but I would need a photo of the marks to research further.
Yes, it could be 18k gold, what makes me suspect it is 18 kt is the millesimal value of .750 tha also appear on the bracelet. The marks don't sound like British Hallmarks.
If you examine the bracelet under a jeweler's loupe at the places that have received the most wear, if it is gold plated, you may be able to see the tell-tale signs of gold plating, ie. peeling, flaking wearing away of the surface layer of gold. Some pieces are exceptionally well done and hard for the untrained eye (and the trained eye) to tell the difference.
You local jeweler can acid test to determine if the bracelet is solid gold or not. Good quality digital gold testing equipment can also determine if it's solid gold, even down to the gold purity value.
