Hello, I believe the basic theory of operation for your power supply is described in
https://patentimages.storage.googleapis.com/fe/72/1b/590040789fc131/US5013973.pdf
The little sticker marked "10 93" may well indicate it was made in October, 1993.
You should also be able to see date codes on the circuit's components too.
I don't think you can change the flash pattern on this power supply...sorry
. Its fixed at "Comet Flash".
https://whelen-engineering.com/install/132/13217.pdf describes how to upgrade older "edge" power supplies to an SL6 which had a few more patterns available.
Yes, it seems if you haven't run the power supply in a long time, the capacitors (condensers) can require "re-forming". This occurs as they run but quoting from a Whelen aircraft power supply manual:
"WARNING: Strobe light power supplies are meant to be used, not to
remain in an inactive state. Use them at all times, this will improve their
proper functioning. Any strobe light power supply that has been out of
service for a long period of time is subject to failure because the elec-
trolytic condenser loses the polarity formation. A strobe light power
supply not having been used for one year or longer is vulnerable to
failure, applies to 1993 & older units.
If this is the case, it is recommended to start operating the system on
a voltage that is reduced by 25 percent for 10 to 15 minutes before
putting the power supply into normal service. This will prevent over-
heating of the condenser while they reform. If the power supply, after
a long period of non use, is operated at full voltage immediately, there
is an excellent possibility that the condenser will become overheated"
Hope this helps!