the chrome Brooks uses is awesome, you might be able to just steel wool it to bring it back.
i dunno what the "73" stands for. the B73 saddle is completely different from what you have. it has 3 giant springs on it.
your's looks like a B72. it'll say it on the side, stamped into the leather, if you can still read it.
Brooks recommends Proofhide, i think. i've used ordinary baseball glove oil from Ace and it does a great job, makes it nice and soft. a coupla problems, though.
one, it's gonna turn every pair of pants you own brown. it'll wash out of jeans, but anything lighter will stain. (that's why spandex bike shorts are black
two, your seat looks kinda torn up at the front rivets. it'll end up tearing eventually, but softening it might help it along.
you don't need to soften the front anyway. a lot of people just do the back, where your backside goes.