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Frank
Whoever advised this has obviously never tried it recently.  I’ve frequently tried to solder 3xPP3 Duracell batteries in series to power my 28V Kollsman, and its quite hard to make the solder stick.  Too much heat and you soon melt the internal connections, and 9v Duracell PP3s arn't cheap.  AA batteries are slightly easier to solder if you don’t mind a bit of light filing first.  However, look at the date 1974, and the forms might have been printed as far back as 1962 when C Plath was acquired by Litton, partly I suspect to manufacture the LN-3 Inertial Navigation System in Germany for the German Air Force F104-G.  They might be talking about carbon zinc batteries. AA batteries were standardised from 1947 when they would nearly all have been carbon zinc dry batteries.  At touch of solder would have been putting 60% tin 40% lead into bed between a brass + top and a – zinc bottom for the original batteries, or between tinplate top and bottom for so called sealed batteries, very cosy in a salt laden sea fret.  Well, that's my suggestion.  As usual, I could be completely wrong.  DaveP