OH, those pics were exciting. Of course I opened the battery compartment at once. No holes or screw ends to see! Probably a matter of scale length? My screws of the tailpiece are above - or the battery cavity is lower as the bridge - how you look at ;-)) My Series I is 34 length.
But the good thing is that I took out two very old batteries I forgot. I used them before I got the 220 --> 110 Volt adapter to use the old power supply which came with the bass here in Germany. I'm glad the batteries didn't drain off.  
Now I'm waiting for the new Alembic screws.

Back from Bassil's, they didn't have anything that was an exact replacement - in stainless or steel. So, the more I consider this, I may just go with the screw/nut arrangement...something I didn't like when I removed the screw to take to the hardware store was that I noticed the center screw is angled - in the wrong direction, towards the headstock. That means there is torque from the tensioned strings pulling on the tailpiece. I can't say I can see that it has moved, but, well, stress is stress. I need to evaluate all this but I have to gig this entire weekend, so..early next week.
 
Harald, good luck with screw remains extraction and here's hoping the new ones work well.
 
Michael, I'll have to come pay you a visit. I'm close to Adams JH.

I rather think that the nuts are on Kenn's bass because the top was deemed too thin to anchor the wood screws. I would not recommend that modification if your screws are anchoring the tailpiece well, which it seems they are since the tailpiece hasn't yet flown off.  
 
What I would be more concerned with is the removal of the tailpiece for cleaning and not filling and drilling the holes. Certainly just leave them the way they are for now and email me your mailing address. I can send you the screws you need. Just make sure you fill and drill when you replace them.

This is just a little trippy, Kenn, Kenn here.  I also opened the battery cover today and found your pic could be my '76 Omega, Maple/Walnut neck, Series I.  I also have the same nuts and bolts.  I believe they are original, I have had my bass since '78.
 
Kenn

Harald,  
 
Two years ago I bought a '75 Series I guitar with the same problem. At the time, I figured that a previous owner had glued the screws in place, and some other unsuspecting previous owner tried to unscrew them! Needless to say, I was too chickens*&t to attempt to extract & dowel them myself. I guess we can take consolation in knowing that all of us lucky enough to own a vintage Series instrument will sooner or later have to go through this!

Thanks Mica!
 
Lenny D.

Just a short note that the repair went well and # 76 278 is grooving again.  
Thank you all for the help an Mica for shipping the screws.
 
Harald

Congrats!!