Another possibility is that they are forgeries. There was a scandel in Edinburgh in the 1820's involving the Liverpool silversmith John Sutter.
Sutter served his apprenticeship in Edinburgh under Charles Dalgleish. Another apprentice serving under Dalgleish at the same time as Sutter, was Alexander Dick who left Edinburgh in 1824 for Australia, and was soon in trouble with the authorities there. Dick was known to use a pseudo Edinburgh town mark on his colonial wares.
I'm not suggesting these spoons are the work of Dick or Sutter, only to say that there are several possibilities as to their origin.
As for references to Indian colonial silver, which is, as you suggest, is another possibility, I doubt if you will find better than our own on the web.
although quite new, it is growing all the time. In book form, Wynyard R T Wilkinson's 'The Maker's of Indian Colonial Silver - A Register of Europeon Goldsmiths, Silversmiths, Jewellers, Watchmakers and Clockmakers in India and their Marks'
is by far the best.