I'm not sure the "Yarborough" knife is technically an "issue" knife. The term "issue" indicates equipment that belongs to a unit, is issued to each soldier on a "hand receipt" of some sort, and when the soldier leaves the unit, they turn the equipment in and receive credit off of their hand receipt. If the equipment is lost or damaged, the soldier signs a "statement of charges" where the cost (minus depreciation) is taken out of their pay, or the soldier goes to the "Clothing Sales Store" and buys the item to turn in (if the clothing sales store stocks that item), or refuses to do either and a "Report of Survey" is initiated where an officer investigates the circumstances of the loss and makes someone accountable.
This knife is given once to each SF trooper upon graduation of the qualification course -- their name and knife serial number are recorded -- but I don't think they have to give it back when they leave the service, or account for it in any other way.
It is a little like the "kit" a General Officer (at least Army type) gets upon being promoted to BG. They get several "GO" type items (black belt with gold buckle, red flag with a star, etc.) including a handgun of their choice (from a small list I presume). Those GO's I am familiar with chose a Colt Officer's Model in .45acp. They did not have to give it back upon retiring.
If I were "Q" qualified, I would keep the Yarborough given upon graduation, and purchase a standard model to use. This would keep the issue model in "collector" grade while still having one of the best knives to use in the field ever built.
My thoughts only.
Bruce Woodbury