[The Philpott]

The last 3 (or 4) digits in the serial number on the scale plate indicate the date of manufacture- it is a case of peering into the glass, looking slightly downwards.
3500-1147 would indicate instrument number 3500 made in Nov.1947.

If it's quite an early meter the voltage shunts are likely to be windings not resistors (and are thus more susceptible to failure.) A DMM with manual ranging is the best idea for checking them as a medium resistance range can be selected to avoid the possibility of *overloading the meter movement should it become energised by the DMM. (*Unlikely with a Model 7 Avo, but nevertheless..)

As regards the leaf switches, they can either be dirty, worn or misaligned. I don't know the constituents of Deoxit so can't comment on it. If contacts are merely dirty what i do is run a little strip of the cardboard from inside a loo roll thro' them, (dry) then soak it in contact cleaner such as isopropyl alcohol,run it thro' then repeat again with it dry. It's possible to rotate the selectors on the front of the Avo to close the contacts onto the card as they're being cleaned.

Should the contacts be misaligned or worn it's usually possible to carefully bend the offending leaf/leaves to make proper contact, but cleaning must be done first to exclude dirt from the equation.

It's not all bad news, some meters which have this sort of fault will have been sidelined and put aside decades ago, with the result that other moving parts have not worn out through over-use.

Dave