So I found a source for the proper reversing Underwood bichrome ribbons with the grommet and after ordering a couple decided to offer my still good uncrommeted bichrome ribbon to a friend with a portable with the red/black ribbon as his machine badly needs a new one.
I asked if he wanted it and he said he did but wasn't sure if his machine took bichrome... I felt kind of bad explaining the obvious that "bichrome" simply means two color. Lol
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Some say that certain typewriters must have the grommet to reverse the ribbon travel. All you have to do is just tie a knot about six inches from the end on both sides, and you'll have the same thing, whether it's bichrome or unichrome.
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I buy all my ribbons with the eyelet (all black since I intend to use them for writing and not for display). And then, if the typer doesn't use an eyelet, I just snip off the end and poke a hole in the end of the ribbon for the little arrowhead hook. I would think tying a knot would leave a pretty big bump on the ribbon spool. But either way would work. It's all about getting a fresh ribbon to run through it to make nice, crisp, dark characters.
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I have an eyelet setter and some eyelets so I could just as easily add some if I got ribbon that didn't have any