Hi Gary,
It IS explained in TCR-6 on p. 116. Look at the 3 $1 chips.
The 1st, N1827 is the authentic one with no inserts.
The 2nd, N1826 has 4-BROWN inserts & is marked IMITATION in
the description column and has an ORANGE denomination.
The 3rd, N1828 is the same as the 2nd except it has a RED denom.
If this is not clear enough, let me know.
Allan