This was a a great bit of technology for Bible translators in the 1960s and 70s. It’s a typeball for and IBM Selectric typewriter. Typical typewriters had lots of little arms each with a slug containing the shape of a letter of the alphabet. To get the special letters we needed, we had to have special slugs made then unsolder the standard slugs and replace them with specially made slugs. The typewriter could then only be used for that language.
The Selectric made this easier. We could have a typeball made with any characters we could design and it just clicked on place. By clicking a different typeball in place, the same typewriter could serve many languages. IBM even made a typeball for dance moves.
Technology has moved well beyond the Selectric. But there’s a constant – technology companies continue to make things that help Bible translation and make it easier and cheaper for people who speak small languages to print and read things in their languages.
Heart Language 
Hi Ed, We used those in Viet Nam. I had learned to solder special characters on our standard typewriters, but never learned how to make changes on the Selectric balls. Fortunately, there were others who did.
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