OK, here is what I would do.
First, look at the screws that attach the mount to the wall. Do they have hex heads, or common screw heads. A hex head would indicate that the mount was attached to studs with lag bolts and is likely OK. Common slotted or phillips heads would indicate it was attached to the wall with wall anchors and is probably not OK. If they are hex head, the next step is to look for the number. If there are only 2, and they are in a vertical pattern, that would indicate a light duty mount for a 32-37" TV and would only be designed for 30 pounds or so. I wouldn't use it. Besides, this sort of mount would have a small bolt pattern on the TV side. If it has 4 bolts in a rectangular pattern and a hole pattern that fits your TV (likely VESA 200) it will probably be OK, and I would try it.
Go to the local hardware store and find bolts that fit. Probably an M6 or M8 at 1.5" long.
BTW, the TV does not weigh as much as you say. The spec sheet says 41 pounds is the shipping weight in carton. The actual weight without stand is 26.5 pounds.
I am not a big fan of articulated mounts. They put a lot of stress on the wall, and people tend to hang off of them. You will be OK if you keep it close to the wall, but if you extend it, be very careful. Do not leave it extended when not in use. Only extend it as far as necessary.