Yes, for 10 days, and it stops showing as available to anyone else during that window. But the hold starts when the cash difference is charged, not when you tell us your plan. Every card here is one of one: holding it on an intention would take a unique item away from every other buyer on the strength of nothing.
If your card never arrives, or the slab does not pass authentication, you choose. Pay the remaining balance in cash inside the window and the order completes as normal. Or cancel — the cash you paid is refunded in full and the card goes back into the catalogue. Either way your card is returned to you insured, at our cost.