Domino

By cataloging all 27 visible tiles against a standard double-six set, the [6, 1] domino is the only one not present in the image.

The domino [0, 0] is missing from the given set of 27 dominoes, as it is not present in the image.

By systematically cataloging all 27 visible dominoes in the image and comparing against the complete standard double-six set of 28 unique tiles, the domino [4, 4] is not present. The double-four (4|4) domino is the missing tile from the set.

Going through all 28 possible domino combinations in a standard double-six set and comparing with the 27 visible dominoes in the image, the domino with values 0 and 3 (blank-3) appears to be missing.

Scanning the 27 tiles, every double except the double-six appears; there is no tile showing six pips on both ends, so the missing domino is [6,6].

In a standard double-six domino set, each number from 0 to 6 appears exactly 8 times across the 28 tiles (7 dominoes per number, with doubles counting twice). By analyzing the image and counting occurrences of the number 0, I identified that the set contains [0,0], [0,1], [0,2], [0,3], [0,4], and [0,5], but is missing [0,6]. The domino [0,6] would have one blank half and one half with six dots (arranged as two columns of three dots). Counting the occurrences of the number 6 confirms it appears only 7 times instead of 8, verifying that the domino with 6 and 0 is missing.