Missing Tesla patents...

I was looking at a list of Tesla's patents and I noticed something strange. Up to about 1900-1901, he managed to file about half a dozen patent applications per year. Yet after 1900, the number of applications dropped off and during 1902-1908 there were 0 filed, then 2 in 1909, 1 in 1913, 1 in 1914, 6 in 1916, 1 in 1921 and the last 1 in 1927. His biography doesn't say anything about him stopping his research after 1902 so I can only assume that he continued to do research, which is confirmed by the six applications he filed in 1916. So what happened in the other years when there doesn't seem to be any patent applications? My guess is that he DID file other applications, which were granted and which the government classified when he died.

I wonder if a patent by patent search for those years would turn up some missing tesla patents? Patent searches are easy to do at www.pat2pdf.org but searching a range of patent numbers would be very time consuming. If anyone has a lot of time on their hands and is interested in maybe bringing Tesla's forgotten discoveries to light, then I would suggest getting a list of Tesla's unclassified patents and pick one of the patents that were filed in the years I described above and work forwards or backwards from there. Who knows what might no longer be classified and waiting to be rediscovered?

I've got a nice, leather-bound volume supposedly containing all of Tesla's patents. When I get home I'll try to remember to survey it and see if I can see any obvious gaps, both in dates and in types of devices he was working on in any given period.