> Are these germanium or silicon?

Silicon, as far as I know
=20
> What would be the advantage of using the TO-18 package over
> TO-92 package?

A little easier to heatsink ? Circular clip-on transistor radiators used
to be quite common to see on boards (in the olde days of RCA-
and Texas-branded TO-5), not so much these days

One not-so-obvious use of a TO-18 package is that you can cut the
top off to expose the die and use it as an opto-transistor. Works
quite well. Can be done with a TO-3 too, although it's not very
good because a power transistor needs a lot of base current

Joe
--=20
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