In keeping with having a Maker's Mark, I have always encouraged folks to also put a date on the items that they put their time and efforts into as years from now people like seeing just how old something is and how it has lasted over time. Plus it's interesting to see how your progress has been over the years.
Here's an inexpensive set of number stamps;
Number stamps
One of my favourite memories regarding date stamps was when I made a Sebenza sheath for a fellow out west, he asked if he could call me when the package arrived and I said sure I guess so. The time came, package arrived and he called me, while I was on the phone he opened the box, took out the knife/sheath and he was pleased, which I was glad to hear

and he handed it to a friend that was there and I could hear him in the background going over how secure the sheath held the knife and then he looked on the back and exclaimed "$5.00 for this?" and the owner said "no silly, that is the month and year, May 2000" which was stamped 5-00 and he said "why would he stamp the price on it??" lol I will never forget that phone call.
But I digress, I think anything that you put your best effort into should have your maker's mark and I would say at the very least what year it was made. My daughters loved to draw, one was especially talented and is now a successful tattoo artist and I stressed to them to always sign and date their work.
On my sheaths you'll find my G2 which stands for Gary Graley, the G2 was a nickname one of my old bosses gave me many years ago and has stuck.
Then the month and year, earlier years I would use single digit for the months 1-9 now a days I do the 01-25 type thing for the month and year.
And lastly a Right footprint, which is meant to remind you that when you wear it to always put your right foot forward in all you do that day, just something that I thought of years ago. I remember one person asked about the footprint and why it was there, I told him I was sorry as the sheath fell to the floor while I was making it and I accidentally stepped on it
110back by
GaryWGraley, on Flickr
Untitled by
GaryWGraley, on Flickr
This dating thing could/should also be on knives, maybe just the year, it would help the owner/future buyer to know how old a knife is. Case knives have a tang stamp code to help understand the year that particular knife was produced, which is a pretty complicated thing for them to do but one that they felt was a necessary feature for their knives as they had the foresight of how collectible their knives would become and how valuable it would be to know just what year the knife was made to a prospective buyer.
G2