The Slotlock Holder prevents type from being inserted upside down.  It is available in both manual (H) and press (P) applications. Press models have 1" diameter x 2" long shanks as standard.
Specials can be made. Sizes from 1/16" to 5/32" are available in various type  capacities.
See above table.

MODEL MODEL 1/16 3/32 1/8 5/32
H-120 P-120 12 8 6 -
H-121 P-121 15 10 - 6
H-122 P-122 16 - 8 -
H-123 P-123 18 12 9 -
H-124 P-124 20 - 10 8
Typical Marking Blanks