Clock details

There is an old grandfather clock on the landing at MaggieD's Mums old house. Neither of us know anything much about it but the painter-work on the dial may give us some clues. The scene above shows sailing ships exchanging fire with and fortifications. At least one of the ships is flying the Union Flag and the fort shows the old Stars & Bars. The last time there was such serious unpleasantness between our two nations was 1812. Might that be a pointer? Another thing I see is that Red Ensign. It seems to be a pre1801 pattern. Another clue?
The makers name looks like Robert Robertson, Glasgow. I think there was a clockmaker of that name in Glasgow working in the 1820s. Any blippers who have any knowledge of old longcase clocks out there?