We've looked at it. We've scrutinised it. We've tried to read it. We've done all those things and we are still absolutely non-the-wiser. Whatever it is it is definitely from 1878 and we are convinced that it is something to do with a local drainage board but if it is then it must be written in a secret code known only to the drainage board employees of the time.
No. 1 P. St. F. 30. 1878. Well we think it says '30' anyway.
Just where are Holmes and Watson when you need them?