9 C.F.R. § 327.26
(a) When import inspections are performed in official import inspection establishments, the official inspection legend to be applied to imported meat and meat food products shall be in the appropriate form 1 as herein specified.

For application to cattle, sheep, swine, and goat carcasses, primal parts, and cuts, not in containers.

For application to outside containers of meat and meat food products prepared from cattle, sheep, swine, and goats.

For application to horse carcasses, primal parts, and cuts, not in containers.

For application to outside containers of horsemeat food products.

For application to mule and other (nonhorse) equine carcasses, primal parts, and cuts, not in containers.

For application to outside containers of equine meat food products.
(c) When products are refused entry into the United States, the official mark to be applied to the products refused entry shall be in the following form:

1 The number “I-38” is given as an example only. The establishment number of the official import inspection establishment where the imported product is inspected shall be used in lieu thereof.
[51 FR 37708, Oct. 24, 1986, as amended at 54 FR 41049, Oct. 5, 1989]