If it's a 336A, it will indicate this on the barrel. Most 336 models will have some discriptive nomenclature such as "A", "SC" "CS" etc. Some do not, they simply have the model number "336" only. Not really sure why Marlin did this. I'm not not looking at any reference sources but I believe this model 336 was made in the 60's and 70's, does not include the cross bolt safety and is equal in value to any other comparable model.
I almost bought one a couple weeks ago for $225 OTD. I may go back and buy it yet.
At any rate, most any 336 you get will be a quality firearm and will offer many years of great shooting.
SS