Word-Counter for Typewriters

Any user today of word-processing software knows instantly how many words a document contains. Could similar information be obtained for a typewritten document? Certainly!

The US Patent Office features several documents for similar devices, but I'm not sure they were ever produced. They had the theoretical advantage of also being hooked to various punctuation keys, so that when you hit such a key, the counter would also recognize the end of a word, as well as with the space bar.

Source.