grep 'FW\-JJT' btl.txt | more
or
grep 'FW\-JJT' *.tag | more
The first step here was to look at the list of tags for one that looks like it would be uncommon, then use grep to find it in the corpus. Using the first command above, the category that this tag appears in (J) is evident from the line code at the beginning of the sentence (|SJ57:49), where the J indicates the section. Using the second command, the category is doubly represented: First in the line code, and second in the fact that grep first returns the name of the file it found a match in.