To the OP, it is fun finding pearls out there, ain't it? I picked up a like new Marlin 336 at a farm auction one time in gorgeous condition, a very little wear around the ejector, otherwise in great shape. I was pleasantly surprised to find it was made in 1952.
When I sold the ranch, I sold the rifle, and was filled with regret as I handed the buyer the rifle. So, I did what any of you would do in a similar situation - I went out looking for another. And I am pleased to ay, I found one. It is in rougher shape than the first was, but has one thing going for it - it was made in 1948. BTW, that is the first model year for the Marlin 336.
So the finds are out there, and since so little cash was involved in yours, I would say - Congratulations!