Sheffield Assay Office used from 1780 until 1853 a special form of their hallmark for items which required a smaller hallmark in which the crown and date letter were combined into a single punch. As Trev has said this is the version created for 1829.
Sansom & Harwood did not register their mark with the Sheffield Assay Office until 1833, but as there is no 'S & H' mark recorded at that office prior to that date, I can only assume that there was an earlier unrecorded entry for that firm.
Cruet stand is the correct designation. It's not intended for condiment dispensers of the size we use nowadays but for the larger bottles for oil, vinegar, spice casters, etc which were essential for fine living 200 years ago.