1780 8 Reales Halved With Tortola Stamp

None of these counterstamps are really common, but the TORTOLA stamp is one that comes up more frecuently.
It is also heavily counterfeited.

I am not an expert in West Indies counterstamps, but as far as I can tell, the collectors looking for the real thing pretty much doubt anything they see, and even buying a slabbed item is somewhat of a leap of faith for them. Sometimes even the stamp types found on the coins in the big collections (Pridmore, Gibbs, Roehrs, etc.) are doubted.

I get the impression that forgeries made for collectors up to completely invented stamps (and histories) date back a very long time and have made access to the field rather difficult.

In any case, a picture of the item in question would definitely help.

Thinking my strike may be on the weak side. I can't find other stamps like this one. If this is counterfeit they sure did a good job..and used silver

A couple of questions please.
How do you know it is silver, did you preform a specific gravity test on the coin?
Did you examine the surface of the coin under magnification? In your photo my first thought was the coin is cast, detail look mushy and lots of surface distortion.
Tourist shops in Florida used to sell sets containing an 8 reales, a half cut 8 reales, a quarter cut 8 reales and am 1/8th cut 8 reales, all bearing the "Tortola" counterstamp. You could also buy the set without the counterstamp. ( I still have my set without the counterstamp and a fellow collector in our local coin club has the set with the counterstamp, we should do a display sometime) I would be very careful in evaluating that coin, the $1 you paid might be true value.

Disappointing but expected

Compare the detail on your coin to the coin I am posting, look at the difference in the detail of the coin. Cast counterfeits like your tourist coin have very mushy details and after looking at a couple thousand of these over the last 40 years, you get good at noticing things like that. I also posted one of my full sets of these tourist coins, this set has several counter stamped, I also have a set where they are all counter stamped and a set where none are counter stamped.