Domino

After listing and comparing all 27 dominoes in the image against a standard double-six set of 28 tiles, it was found that the (0, 5) domino is the only one missing.

The excluded domino is number 3 and 3

After carefully cataloging all 27 dominoes visible in the image and comparing them to the complete set of 28 dominoes in a standard double-six set, I can identify that the [1,1] domino (double-one) is missing from the image.

I inspected the 27 tiles in the image and found every pair combination from 0–6 except the double six (6,6), so the missing domino is [6,6].

By counting the occurrences of each number across all halves of the 27 dominoes, numbers 3 and 5 each appear 7 times, while all other numbers appear 8 times, indicating the missing domino is [3, 5]

By analyzing the pip counts across all visible dominoes, digit 0 appears exactly 7 times (in dominoes [0,0], [0,1], [0,2], [0,3], [0,4], [0,5]) and digit 6 appears exactly 7 times (in dominoes [6,6], [6,1], [6,2], [6,3], [6,4], [6,5]). In a complete double-six set, each number should appear 8 times. Since digits 0 and 6 each appear only 7 times, and all other digits (1,2,3,4,5) appear 8 times, the missing domino must be [0,6]. This is confirmed by locating all other 0-x dominoes and all other 6-x dominoes in the image.