Domino

By systematically analyzing all 27 visible dominoes in the image and checking against the complete set of 28 double-six dominoes, the domino [0, 0] (double blank) is the only one not present. All other combinations from [0, 1] through [6, 6] can be identified in the image.

After cataloging all 27 dominoes shown in the image, the only tile missing from the standard double-six 28-tile set is the [0, 4] (blank and four) domino.

The excluded domino is number 3 and 3

After counting the pips on all 27 visible tiles, the numbers 2 and 6 each appear one fewer time than they should (7 times instead of 8), so the missing domino is 2-6.

Analyzing the complete set of 28 double-six dominoes and identifying the 27 present in the image. The 0-series dominoes [0,0], [0,1], [0,2], [0,3], and [0,4] are all visible in the image. The domino [0,5] (blank on one half, 5 pips on the other) is the only one missing from this series and from the complete set. Other high-value dominoes such as [1,6], [2,6], [3,6], [4,6], and [5,6] are present, while [0,5] cannot be located in any orientation.