I miss the Curtis 8044 keyer ICs.  I built several keyers in my early ham career using that IC and it performed flawlessly.   Designs based on it had a simplicity that really appealed to me, and worked nicely.

After production ended, I watched the hamfests for old keyers I could pick up inexpensively to get the Curtis chip.  But I rarely encountered them. 

I eventually focused my keyer projects on kits that used PIC microcontrollers.  Such as

These designs allow memories and other advanced features (such as keyboard keying) but it was fun to recognize that they were all striving to do the basics as good as the Curtis keyers.

Attached is the IC application note.