Collectors in certain fields (numismatics, royal memorabilia, buttons, etc) are aware that Royal households have adopted certain heraldic symbols including crowns and cyphers. So too have non-royal sovereign states (Republics). A heraldic crown does not necessarily depict a physical crown; it may be purely symbolic.
The cypher is usually the initial(s) and title of a sovereign ruler. In Commonwealth countries, this followed on from its use in the United Kingdom from the early Tudor period (1485-1603). After Henry VIII it included the letter R for Rex/Regina, and after 1877 the letter I for Imperatror/Imperatrix. Cyphers have also been used by Sultans and European kingdoms.
The depiction of heraldic crowns was not regulated during Victoria’s long reign. As a consequence, the depiction of the “Queen Victoria Crown”, so called by common usage, varied considerably. Sometimes it seems to have been based on St Edward’s Crown, sometime on the State Crown which was newly made in 1838 for Victoria’s coronation. This had a square shape with a slight dip in the centre. (The St Edwards Crown, weighing .2.23 kg (4.9lb) was too heavy for the Queen to want to use for the coronation.)
There were actually two similar state crowns used by Victoria, as seen below:
Victoria did wish to continue wearing the state crown when she re-entered public life after Albert’s death, as she found it uncomfortable, and so had a small diamond crown (similar in form to the Tudor crown) made in 1870.
Perhaps this is why the crown depicted on this button looks like the the small diamond crown as opposed to the “Queen Victoria Crown” that we expect in that era?
Cossum (page 9) labels this as a Victorian Volunteer Service c.1875 button.
Despite the similarity, it cannot be regarded as a “Tudor Crown” as the stylised image of the Tudor Crown was not adopted until 1902 for use on insignia, etc, when His Majesty pointed out that “on accoutrements, colours, buttons, etc., there are no less than six or seven totally different pattern Crowns. Some of them are Foreign Continental Crowns ; others are different deviations of the British Crown. His majesty now wishes one uniform Crown alone to become the sealed pattern for the Service, – the Tudor, “Henry VII” Crown, chosen and always used by Queen Victoria personally; all other patterns are to be abolished.”* It seems Victoria preferred this type of crown used for heraldic purposes, but it had not been enforced. The above button dates from 1875 when the motto on the button, “Aut Pace Aut Bello”, was adopted.
For another button with a “Tudor” style crown, see http://www.austbuttonhistory.com/uncategorized/24th-march-2021/
*From a letter written by a secretary of the War Office in May 1901.