Yes, the 5th Garde Regiment, it is a nice muzzle cover. These Garde marked are more desirable and much harder to find, though selling them for what they are worth isn't so easy. Generally collectors are rather miserly on muzzle covers, typically they will pay $100 or so for a muzzle cover but a really nice unit doesn't appreciably increase the price many will pay for it, which is odd because bayonets collectors will often pay double or more for the right unit marking on a bayonet.
I have sold quite a few muzzle covers, rare is the day that one sold for what I thought it worth, even a Garde Jäger muzzle cover took forever to get a good price for and not what I expected either... oddly Simson lids (e/6 etc..) seem to draw more interest, but even they have difficulty over about $200, which is a good price compared to how much a Garde marked lid should pull. Garde marked are far and away more rare than an Simson muzzle cover. They made quite a few and I own and have owned quite a few.