And here's a Flexowriter.
Their main use was to eliminate repetetive typing chores, like form letters, invoices, etc where you had to produce numerous identical originals but only change certain "fields" within the document, such as the persons name, or a figure, whatever.
How they worked was you would put in your form or piece of typing paper in the carriage as normal and at the place where you were going to begin typing.. i.e. Dear Mr. Gansky, you would press the button on the right and as you typed it would create a paper tape in the unit on the left side rear. After you typed the word "dear" you would again press the button down the oppose way and the tape would stop recording and you would type in "Mr. Gansky", then you would press the button again and start typing your letter, each time you came to an area that might contain different information for another customer you would stop the tape, type in the current customers info, then start the tape again. When you were done you know had a "master tape". You would stick the starting end of that tape in the "tape reader" left side front, position your new piece of paper in the carriage where you wanted the machine to start typing and hit start, it would type "Dear" and stop, you would then type in the next customers name and hit start and the letter would continue typing automatically, stopping at each point where diffferent infor for that customer was manually typed in. Very effective for its day. You could keep the tapes on a spool but rather than use tapes you could use punch cards that folded up accordion style and they had special holders for those making them easy to file.