Okay, it seems to be really interesting for you to know how it works. I'll try to explain the principle how the measuring devices work. Hope you'll understand it, because I don't know if I find the perfect words in English for the parts...

Here I show another measuring unit from the manufacturer "Josef Feichtmaier of Geiselhöring". It is approx. 60-70 years old, one of the last constructed devices. After WWII they weren't anymore demanded. There were enough devices in the shooting clubs and schuetzen societies of former decades. If you don't throw it down, it will work for ever without problems. 
That's German engineering! *cheekysnicker*    

The measuring step by step in details:

Step A: One places the paper-bull carefully with the impact hole onto the mandrel without perishing the hole.

Step B: Afterwards one places the "holder" (#1) onto the mandrel. The holder has a cone-shaped pin at the bottom. With this pin the paper-bull is centered on the mandrel.

Step C: Inside the holder, there is a spiral spring, so that one can pull it down to hold it in tension.
Afterwards the dial indicator (#3) is set to "zero". The paper-bull will be turned carefully and slow by the holder. 
The measuring starts, when the "highest point" of the out of center turning paper bull touches the slide gauge (#2) towards the dial indicator.

Step D: At the dial indicator there are two scales to read the measuring. 
On the horizontal scale (#4) one can read out the "100's". One can see that the needle is very short just under the 200, it's only shown one entire "100".

Step E: On the round scale (#5) one can read out the detail value. A "92" is indicated. Both values (100 + 92) are added to the sum of 192, this is a so-called 192-Teiler.

The impact hole is 1.92 millimeters (0.075 inches) out of total dead center of the paper card bull-target.

I hope you understand my description of that particular matter.    
If there are any questions, don't hesitate to ask.

         Biggi.

Biggi - Thanks Kindly for the Teiler bull's eye measuring machine picture details and the words how it operates.
It all comes together in my head now and understand the measurement procedures clearly ...
Quote:

With the complete center being 5.cm/1.96" and the inner being 2.5cm/0.98" ... I also understand now why the diopter pinhead foresight on Schuetzen rifles is so darn small.  When I removed the blade foresight on my rifle and replaced it with the pinhead, was totally amazed at the accuracy one could obtain if they were a skilled offhand shooter

Again - a very informational and educational thread!

Hi JohnBoy.

Just remembered that they had also turnable foresights in the old days.

Instead of changing the complete foresight, they had the possibility to choose the desired kind which was convenient for the current target.

                  Biggi.  

Good Morning JohnBoy. In Bavaria it' already late afternoon...

Makes me a kind of proud that my technical English is understandable.     

In Germany one cannot buy any of these old parts for Aydts or Martinis. There is nothing left from the old days. Nothing is produced since the 1920's, maybe early 1930's.

If we need a spare-part, we have to make it on our own. One needs a talented precise mechanic guy who likes to tinker fitting parts. Because all the parts are soooo different, also in the old days it wasn't possible to buy something out of the shelf - in the most cases. 

And if something is broken today, one has to bring the defect part to the gunsmith (including the whole rifle) that the gunsmith can work on a replacement part which fits exactly. The same with those Aydt springs. They are nearly all completely different. If you find a gunsmith who makes one for you, let make three at this time. Maybe you'll never find again a person, who wants to make an Aydt spring...
 

Last week at a match, the firepin of my Martini was broken. And I needed the rifle again five days later. So I found at that match an old man, a nice schuetzen fellow, who was able to make exactly that needed broken firepin in a very short time. So I got back that stuff and won the next match.  

That's the only way it works with those old rifles. You really need fellows who can help...

                   Biggi.  

HHhhhmmmm, at the moment I don't know, if there is still interest in reading something about the old German ways to measure bulls?!?! No feedback anymore?


Okay, I may go on, there are still some aspects to explain.

Larger papercard bulls are made sometimes out of thin papercard. Also small papercard bulls may get a buckle during releasing it from the target. If this happens, it wouldn't be possible to make a correct measuring. So they invented small plates out of metal or duroplastics, where one can insert the bull exactly for the measuring procedure.

One has to place the impact hole over the slot in the template. Then the mandrel pricks still through the hole. The edge of the papercard bull fits perfect into the recess. And the measuring works much better round the template's edge. 

In the both examples shown above, there are a couple of templates for .22-small-bore and also airrifle and zimmerstutzen papercard bulls. Its also possible to measure 5 centimeter bulls, but at the moment I have no templates for those.

               Biggi.    

The rifle in question is probably a Kessler full stocked Martini style rifle. 

Those Germans are to smart to shoot a bolt action. 


            Joe. 

The pictures show a 98 Mauser #5 and one I owned. Highest known serial number seen so far is #10