The clarity of the image from the stamp depends on the type of surface you are hammering on, not just the stamps themselves. If you are stamping on a table surface it will give way under the force of the blows of the hammer which means the image of the punch will not be crisp and sharp. The best surface for stamping on is a concrete floor (a surface with no "bounce") but since most people prefer to work at a table, a sandbag is used to deadened the force of the hammer blow. Put a steel bench block on the sandbag and strike cleanly once straight up and down.
so it looks like this
item to be stamped----------
bench block ------
sandbag -----
table -----
Your image from the punch will be sharp and clear. As you work the metal it may curve. To straighten it out use a rawhide mallet. Triple stitched to prevent leaking.

3mm