Is it possible to make a blank using a current postage stamps?. I was thinking of the purple heart stamp. I don't cast and most likely never will but would like a couple or so of the stamps.
You can actually make a "stamp" pen without doing any casting. Simply use some type of glue to adheres the stamps to the pen tube, seal with gloss Modge Podge, build to the proper thickness with CA glue, and finally, buff to a shine with micro mesh.
At one point in time, there was a video demonstrating this method on YouTube.
Depending on the style of pen, you might be better off turning a barrel out of ugly (but flat) wood and putting the stamps over them. Just make sure you over turn the barrel to account for the stamps modgepodge and CA