Yes, but what margin does it free up ?  Because on manual margins, it has no effectiveness...

I have enlarged and lightened up your photo a bit.

The CR lever shape of a big, fat tongue-depressor might be a key...
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Pete E. wrote:

Sorry...posted my reply, above, to the wrong discussion thread...

It's not serious for the bad post !
For the rest, I will instead use this subject, which seems more advanced in the answers: https://typewriter.boardhost.com/viewtopic.php?pid=34054

PS: How did you improve and brighten the image ?

Hi Olivier

How about we get back to the original question of this thread. I have had to answer the question about what the Margin-Release (M-R) key does so many times, that I wrote up what I believe to be an understandable explanation of the M-R key function. See what you think:

The MR key gets many people confused as they don't understand its purpose. When you are typing on your computer, you select the page size from the list of pre-set sizes - letter, legal, A4, A5 and so on. Then you set or select the margins on the page and start typing. If you type a word that's going to go over the margin, the word wraps round to the next line down and you keep typing. When you've finished, you save and send to print, job complete.

On a manual typewriter, the page size is set by the piece of paper you insert into the machine, we'll use standard 8½" x 11" letter size for now. You've set the paper guide to zero, the left margin to 10 and the right margin to 75 on a pica (10 CPI) machine and you're typing happily away, then you hear a bell go ding. This bell tells you that you are only a few spaces (usually 4 to 8 depending on the machine) from the right margin.

Because a typewriter can't word-wrap, you have to be constantly thinking a sentence ahead of what you're typing. If you've just started typing a long word when you hear the bell, you know you only have a few spaces left before you hit the right margin and the machine locks up, so you'll have to hyphenate the word at a suitable point and type the rest of the word on the next line.

Some words however must not be hyphenated, the word that comes to mind is "therapist". If you've just started typing that word and you hear the line end warning bell a you type the letter 'T', do you hyphenate to The- rapist, or Thera- pist, neither of which are acceptable. Instead, you type Therapi and the typewriter locks up. Now you press the MR (margin release) key once and finish the word before returning for the next line.

The MR key can also be used if you want to put point numbers in the left margin. Return the carriage to the left margin, press and hold the MR key and move the carriage a little further to the right to where you want to type the point number. Hope this makes sense to you,

Sky