No set number of numbers and letter..
It depends on the brand. It might stand for "Taurus Handgun" if it's a Taurus. What brand is it?
Find books on your weapon with sn data.
Frame and/or butt
What is it (rifle, shotgun, handgun) and who made it? What are the markings/words on it?
Check the receiver and barrel
No specific characters. Glock serial numbers for a long time now have been 3 letters, then 3 numbers.
No
Some manufacturers websites have serial number data available, i.e, Ruger and Browning. Proofhouse.com has serial numbers for Colt Oldguns.net has some serial numbers ArmsCollector.com has some handgun forums.
The number to Taurus customer service is 305-624-1115.
Would need model name to answer.Go to proofhouse.com
Your guess is as good as ours. Serial numbers are NOT unique to one firearm. Send some photos, and perhaps I can narrow it down for you.