Mike Stewart (more recently the founder of Bark River Knife and Tool) was the vice-president of Marble's and was in charge of knife production from August of 1997 to August of 2001. Many collectors agree that the Marble's knives produced during this period were of excellent quality, and mint-condition 'Stewart-era" knives continue to garner prices equal to, or at times exceeding, their original sale value.
Between 1997 and 2000, Mr. Stewart decided it would be useful to have a dating system for the knives being produced, and rather than a mere date stamp, a creative solution was reached - the year of production during this period would be identified by the unique combination of stacked washers. For those interested in these highly-collectible knives, I thought this might be useful: