They are in a circle and there was hand-drawn.
If these are what you are looking for you can get them here
Just unzip the download and Copy and paste the Stamps v12 folder into the following location on your computer:
C:\Users\YOUR USERNAME\Documents\Snagit Stamps\
Eldazey, Like Rick said the stamps are in "C:\Users\YOUR USERNAME\Documents\Snagit Stamps\" folder. you can download the zip file form the link below and make sure that you extract the files in "C:\Users\YOUR USERNAME\Documents\Snagit Stamps\"folder, restart the editor and you will see the letters you are looking for. I have been using these stamps since v10>, they do work in v2018 too.
In v2018 SnagIt made the stamps as .pdf files (like Adobe Acrobat) instead of .png like the older version but the .png stamps do work. you may still be able to download the old stamps from SnagIt website.
Hopefully this helps, enjoy.