Alex Cameron was working in Dundee between 1818 and 1849. His work is easily detected as his mark is unusual being his full name CAM over the top of ERON, sometimes in script form. The thistle was introduced by Alex Cameron at Dundee, similar to that of the Edinburgh thistle. This mark was also used by Edward Livingstone and other Dundee silversmiths. We know of no significance to the "q" but it is known that Dundee silversmiths did use letters in their hallmarks, notably D, C, S and U at least.  It could be that these represent some form of series of date letters. The castle is unusual and would perhaps signify that these tongs were actually assayed in Edinburgh. If they were then the "q" would represent a date of 1822/23.

This pair of tongs is fairly standard for the period, being fiddle pattern with concave arms and a squared bow, with shell like bowls. I have dated them at around 1820 to 1830.