This bottle belongs to a series of intriguing 'coin' bottles carved with the two sides of the Spanish silver dollar which, along with a gold counterpart, were standard international currency in trading during the nineteenth century. Such bottles are usually of rock crystal but are also found in other types of quartz, nephrite, and very rarely, in glass. For a discussion of these coins, see Moss, Graham, Tsang, A Treasury of Chinese Snuff Bottles, the Mary and George Bloch Collection, Volume 2, Part 1, Hong Kong, 1998, pp. 154-157, no. 238.
The present cameo agate version is unusual in its shape; most snuff bottles in this group are circular and as such could echo the exact proportions of a coin. It seems to be a rendition of the Charles III coin, another version of which is seen on a rare blue-overlay glass snuff bottle illustrated by Moss, Graham, Tsang in The Art of the Chinese Snuff Bottle, The J & J Collection, New York, 1993, Volume II, pp. 633-34, no. 385. The profile of the monarch is the same on both bottles, as is the coat of arms on the reverse and the motifs flanking it. However the Roman letters on the present agate version appear to have been lost in translation. The letters around the profile are just portions of the actual inscription that appears on the J & J glass bottle, CAROLUS III on the left and DEI GRATIA on the right. The I beneath the profile on the present bottle appears in place of 1796 on the coin. The I motifs on the reverse are probably just improvisations of the carver to fill the space with a Western emblem. Because of these discrepancies, it seems possible that the carver of this agate bottle was looking at another snuff bottle or object decorated with the Spanish coin, and possibly did not have an understanding of what the decoration was meant to represent.