Letter on slab that I don't recognize 0

[Shadows584]

I have a 1947 S Washington quarter that is in a NGC slab that is graded and labeled as an MS 66T. What does the T stand for? I've never seen this.

[DWLange]

Around 2000-2001 NGC began grading modern (1930s and later) USA coins with the designations T for Toned and W for White (entirely untoned). This was in response to market trends at the time, but the program lasted just a few months, as I recall. If this coin were submitted for regrade or even a simple reholder the T would disappear, as it has already in the Census.

[VKurtB]

So then it’s not “Tickle”? I’m disappointed. 

[EARLY-COMMEM-HUNTER]

I can recall only seeing one “T.”
I’ve seen many with the W and have one in my collection. Anyone can shed some light on how many of these T’s are out there?  I know an exact number is impossible. I’m talking anecdotal as to how many you’ve personally come across??