In my SG-230, it says 5DL on the top of diode. Don't know if that is an ID:
code of sorts.

Yes, that's an ID code.

According to one set of notes I've found, Fairchild use 5D as the code
for an MMBD914, which is a fast switching diode similar to the 4148,
in a 3-lead SOT-23 case. The MMBD4148 would have a 5H code. The two
parts look *very* similar on the data sheets, and from what I've seen
in practice they're interchangeable in most applications.

If this is what you've got, then the pinout is as follows: if you
look down from the top of the diode, with the two-leaded side on the
left and the one-leaded side on the right: pin 1 at the top left is
the diode's anode, pin 3 at the right center is the diode's cathode,
and pin 2 at the lower left is not connected to the diode.

The pinouts are the same for the MMBD914 and MMBD4148.

--
Dave Platt AE6EO
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