This information has been updated with many thanks to Miles Harrison, who has recently published a new book "Exeter and West Country silver 1700-1900".  This is an extremely comprehensive book and can be bought directly from Miles - simply click HERE

Francis Parsons' career is quite complex as he worked with a number of business partners. The dates are approximate but as accurate as we know of:

13th December 1797 - Alone
22nd December 1797 to 25th March 1800 - with Stephen Crees
28th March 1800 to 28th November 1802 - Alone
4th December 1802 to 23rd March 1803 - with John Bennett (only 8 pairs of tongs were assayed (on 4th December 1802))
15th January 1803 to 31st May 1805 - Alone
8th June 1805 to 24th December 1806 - with Joseph Goss
2nd January 1807 to 6th August 1808 - with B Goss
19th August 1808 to 30th November 1810 - Alone
4th December 1810 to 6th August 1814 - with Joseph Goss
27th August 1814 to 2nd November 1815 - Alone
25th November 1829 to 20th August 1831 - Alone

Very often his partnerships are recorded as "Parsons & Co." so we can not actually be sure of any of these start and end dates.

Francis Parsons sent his first work for assay in partnership with Joseph Goss on 8th June 1805. The parcel happened to include some 9 pairs of sugar tongs. All together they had the following tongs assayed:

8th June 1805 to 9th October 1806 - 113 pairs of tongs. Of these 11 pairs of tongs were sent in after 7th August. This matters because I believe that the duty mark was changed to being not clipped and having no cusp from 8th August onwards.
4th December 1810 to 23rd March 1814 - 206 pairs of tongs

Notice that the earlier dated tongs have the maker's mark initials the opposite way around to the pair dated 1813.

Click here to see some tongs by Francis Parsons alone
Click here to see some tongs by Francis Parsons & Stephen Crees
Click here to see some tongs by Francis Parsons & B Goss