I've had another look at the video.

There are no top connections on the AVO.

The model 40 had the same top connections as the later model 7 (ii?)

Since the original model 7 did not have top connections it must be a model 7 unless a variety of the model 40 also did not have top connections, unlikely but not impossible.

No, it is definitely a Model 40.  If you pause the video at 25 mins 54sec you can just make out Model 40 at the bottom.


David

This is worse than train spotting. ?


After adjusting the equalisation, you can clearly see "MODEL 40".




Getting even further into the weeds, it's the Admiralty pattern 47A - see the writing at the top of the scale.


More info here.

Well done Chris, my picture is much more fuzzy.


Should we really be doing this on a summer Sunday afternoon?


David

Is no one going to comment  on the battery in the demo of the mercury switch being a modern one (and rather unlikely use of modern wire insulation too)

I guess to mock up a real wartime one would have required a battery to be re-gutted, and for  10 second shot, not worth it.

So, there is a model 40 that does not have top connections, hmmm.

mapj1:

Is no one going to comment  on the battery in the demo of the mercury switch being a modern one (and rather unlikely use of modern wire insulation too)

I guess to mock up a real wartime one would have required a battery to be re-gutted, and for  10 second shot, not worth it.

Steel encased you mean?

The trouble is that to mock up a real wartime cell would require making up a zinc body rather than a simple re-gut.

I've never taken off the steel on a cell before, perhaps that might be possible?

Is it just zinc underneath?

(That admission gives some idea of how long it has been since I stopped dismantling batteries and cells.)


Of course if we are going to be critical the whole thing looks as if it were made out of materials made yesterday anyway.

I am young enough to have opened the 1970s steel cell HP11 and SP11 type batteries, and indeed there is a waxed paper cylinder under the steel, and then the zinc outer of a normal 'U' type cell.

But nowadays, the alkaline carbon zinc cells that have become pretty much universal are ' inside out ' wrt the old ones, and the anode which always was the high resistance electrode,  is the now one with the larger surface area - hence the much higher short circuit current available from modern cells for a given size 


They'd also have to cool it a lot more to neutralise it with a modern battery - consider the top of the consumer range  L91 Lithium disulphide cell (AA cell 1.5V)        will still run, albeit weakly, at -40C. We specify them for ' awkward '  environments which may get frozen.

Ever ready 1289, need i say more?