Here's a link to an inexpensive kit (or pre-built) 700-Hz sine wave Morse practice oscillator...
https://vakits.com/code-practice-oscillator-kit-w-phono-jack-3768
I don't have one but it meets my criteria for a decent practice oscillator.
Steve WD8DAS
sbjohnston@aol.com
http://www.wd8das.net/
http://af4k-crystals.com
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