By "mainly sold in the U.S." I meant that the Leeds & Catlin Imperial label was originally established as a label manufactured and sold in that country. As far as I can establish it was not initially made as a purely export label. There was no significant UK distribution until 1906 and this early Imperial label existed for about a year before that and during this time it was "mainly sold in the U.S."
It seems that it established as a normal U.S. label, and it is listed as such in Allan Sutton's "American Record Labels & Companies: An Encyclopedia (1891-1943)". Brian Rust's book on 78rpm record labels has 2 pages on the UK Imperial which was established in the 1920s and just one paragraph on the Leeds & Catlin Imperial which does not even mention it was sold in the UK. Don Taylor's "English 78 Picture Book" says: "The American-made Imperial Record is outside the scope of this book".
There is a section on the Discography of American Historical Records site titled: Leeds & Catlin Records: The Leeds & Catlin Labels (https://adp.library.ucsb.edu/index.php/resources/detail/418)
Under Imperial it states: Imperial — First advertised in the June 1905 Talking Machine World, Imperial soon supplanted the foil-label Leeds Records as Leeds & Catlin’s flagship brand. They originally retailed for $1 each but were reduced to 60¢ in December 1905, coinciding with discontinuation of the foil-label line. Imperial’s catalog numbering system continued that of the Leeds foil-labeled discs, with 40000 added to Leeds’ base number (e.g., Leeds 4438 = Imperial 44438). The discs were widely exported to England beginning in the spring of 1906. In October 1907, Sun replaced Imperial as Leeds & Catlin’s flagship domestic brand. However, Leeds continued to produce Imperial records for export to England, reportedly in very large quantities. New Imperial releases continued to appear regularly in the British trade-journal advance lists, but not in their American counterparts. Although Imperial records were still being advertised by British dealers in 1909, it is uncertain whether any were manufactured after Leeds & Catlin began producing double-sided pressings.
I think it's clear that the Leeds & Catlin Imperial was established as an American label since it was that company's "flagship label". However, from the above details it also appears that once the Sun label "replaced Imperial as Leeds & Catlin’s flagship domestic brand" in 1907 the Imperial label became mainly an export label to the UK.
Probably, the reason there's some confusion about whether it's an American or UK label is because it was at different stages of it's life-span BOTH.
After a while on google I found this article {link}. The New York and London adverts imply that both UK and USA issues had the same label style. But under the London advert it states that "London-based Gilbert Kimpton & Company imported huge quantities of Imperial discs" and "In February 1906, The Talking Machine World reported that Leeds had received an order for one-million Imperial discs for export" so I'd question if the earlier statement "mainly sold in the U.S" is entirely correct. Another article on the same site {link} tells us that 'Imperial' was replaced by 'Sun' in 1907 in the USA, so only had a lifetime there of about two years, and also illustrates a plainer Imperial label.
Frank Andrew's longer article on the label published in 2002 is interesting as it refers to specifically British emblems on the label.
"The labels were printed in gold, purple and black and the background depicted the inside of a British monarch’s Imperial cape, trimmed with ermine, draped and drawn into folds, like a curtain, with gold tasselled cords. The titles, and the artists’ accreditations were printed on this royal cape. The whole was surmounted by the Imperial Crown of England printed in gold."
Would the same style of label pattern have been used in the USA?
"IMPERIAL. An American lateral-cut, single-sided discs issued by Leeds & Catlin Co., New York, from c. 1900 to 1909. Imperial was sold in Britain also, for 2 shillings, from April 1906, by Cook's Athletic Co., London." [from an article by Frank Andrews in "Encyclopedia of Recorded Sound in the United States" edited by Guy A. Marco - Frank Andrews, Contributing Editor].
Note that this Imperial label was not sold in the UK until several years after it began in the U.S. so it cannot be a label made purely for export.
Yes, I have seen reports that they were sold in the UK, but it's a U.S. label which was mainly sold in the U.S. It's not a label which was made specifically for export to the UK.
According to the CLPGS Imperial Records in Britain by Frank Andrews & Bill Dean Myatt, this record was in the first series of Imperial Records issued in the UK from April 1906 to 1909.
Manufactured and exported by Messrs. Leeds & Catlin from Middleton, Cincinatti, USA, all were 10 inches diameter single face recordings.
So it seems the disc could be USA or UK issued unless we can find label differences that prove otherwise.