Diode marked "D2S21"?

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I have some THD silicon diodes marked "D2S21" the 21 is written in a smaller font and the 1 has a small dash under it.
I can't find any info on this diode, maybe it uses some uncommon model number scheme?

I also have some small THD diodes marked "0440" the first "04" is written horizontally (the pins would go vertical when reading it) but the other "40" is written vertically, 4 being above and 0 bellow.