The SF-2 wasn't around in the 70's, just the F-2B. We did make Superfilters back then, but they were not rackmounted, they were installed directly in instruments.  
 
Post a picture if you have one available.

Here is how it is described. I think he said it was a rackmount.
 
'vintage alembic 2 channel tube bass preamp'
 
He was thinking $600 which seems too much?

The average price on Ebay for an SF-2 is probably around $400, or maybe a little more.

Dave, that is the description for an F-2B.  $400 is about the going eBay price.  Sometimes they sneak through around $350, sometimes they go to $450.  Oddly enough, all three Alembic rackmount products have the same list price and trade for about the same amount used.
 
I am not sure if there is any benefit or detriment associated with the older models, or how that should affect the price.

I paid $399.00 used through Bass NW for one that Chad descibed as pristine.  I'll be picking it up tomorrow.  More later....
 
P.S. OH BOY OH BOY OH BOY OH BOY OH BOY ETC.!!!

Hollis:
 
    I suspect you will be a very happy camper tomorrow.  Now all I have to do is wait for the maybe broken one to arrive from the e-bay auction, and, if it is broken, get it fixed so my bass player will let me use mine!  You will love it, it is truly an amazing piece of equipment.  Be sure to post your impressions.
 
Bill, tgo

Hi Bill,
 
I'm really looking forward to it.  
 
My best impression is Walter Brennon, but over the web it seems to lose something in the translation......

Hollis:
 
   Ever been stung by a dead bee?
 
  extra credt:  Hey Luke
 
Bill, tgo

Bill,
 
Luke, Pepeno, I catch ya smokin' pot in the house just one more time, you're gonna have to sleep out in the barn.
 
One day I'm gonna climb that mountain...just me and old Rivers, cuttin' down the corn patch...
 
Ba Da Boom!

YAAAAAAHHHHHOOOOOOOO!  This is the sound I've been looking for all my life!  Persuader (3 way Q switch added), or Skylark.  Both are flying high on all cylinders through the SF-2. I can't wait to do some recording through this wonderful addition.

Hollis; is there a link to an MP3 of Luke, Pepeno, I catch you smokin' ...?

Dave,  
 
No link, just fact.... That's just part of a little soliloquy that a few friends of mine and I used to spout. Sorry, when it comes to Walter Brennon I tend to get a little carried away...

Ok, I am thinking the quote was from an old Bogart movie with a boat in it...not Key Largo.... To Have and Have Not?
 
EffClef
 
PS the doc in Bad Day at Black Rock had good lines, too.

To Have And To Have Not featured Bogey as Steve, a 19 year old Lauren Bacall as Slim  (This is where Bogey & Bacall met and fell in love - he was about 45), Hoagy Carmichael as the hotel bar pianist, and the unforgetable Walter Brennan as the lovable rummy Eddie where he kept asking everyone have you ever been stung by a dead bee?  Only Slim (Bacall) knew the right answer:  Bite 'em back.  This film also featured the famous line where Bacall tells Bogey If you want me just whistle.  You know how to whistle, don't you Steve?  Just put your lips together .... and blow.    A must rental if you've never seen it.
 
The Luke/Pepino lines come from the TV show The Real McCoys  where Brennan played Grandpappy Amos.
(I haven't thought of that name in at least 35-40 years and I came up with it right away.  Boy, is my mind twisted).
 
Bill, tgo

The name Walter Brennan didn't ring a bell, but I do remember the character from To Have And To Have Not. He kind of made Bogart look like he was overacting.