It could be soft briar, but hat looks more like a gouged cake layer. Easy to fix.
Take a strip of sandpaper and wrap it around your finger and run that sandpaper covered finger around the inside of the bowl -to smooth out the cake. Your hands will be filthy from the powdered carbon, so do it over a sink or over a sheet of newspaper.
I usually then coat the bowl with honey and then pack the pipe with tobacco. Smoke the pipe the next day, and lightly wipe the bowl interior with a paper towel when the pipe is cool. Some tobacco might/will cling to the wall of the bowl. Load and smoke the pipe as usual, wiping the bowl walls with a paper towel each time, after smoking. Cake will build up very gradually if at all. Too much cake?....sandpaper away the extra carbon buildup, if necessary.
I've been smoking for years and have rarely gouged or chipped away the cake that builds up in my pipes.
Sandpaper, works.