[Joe_G.]

If good data isn't available, it would be fairly easy to run a test to better understand risks. A test plan could look something like this:

1. Place 5 cheap/modern? slabbed cards in cardboard box in oven (boxed just as you would store in safe)
2. Bake at 200F for one hour, pull slab and allow to cool
3. Bake remaining four at 250F for another hour, pull slab and allow to cool
4. Bake remaining three at 300F for another hour, pull slab and allow to cool
5. Bake remaining two at 350F for another hour, pull slab and allow to cool
6. Bake final card at 400F for another hour, pull slab and allow to cool

The slabs should then be inspected followed by popping the cards out and looking for any signs of damage (damage the slab imparts on card). One could also place a non-baseball cabinet cut down to the size of OJ cards along with some paper to see how the two compare at the higher temperatures. Would probably want to include a secondary temperature measuring device placed on the box that you can read during test.

Have fire extinguisher on standby and pick a day the wife is away