The very common hazards in electronics are BeO thermal links and Beryllium Copper alloys used in spring stock and in RF vacuum device construction.
Eimac Varian used to include BeO hazard sheets with most of their valves and I remember long debates as to whether the insulating seals in 4CX250Bs were Beryllium Oxide- I think it was decided that they were not, though the thermal links of conduction cooled versions were. External anodes frequently used Beryllium Copper for better machining- machinists often suffered from lung disease, though it may have been incorrectly attributed to smoking.
Lots of RF power transistors from the 1960s to the 1980s used BeO packaging for better heat conductivity and RF attenuators/loads frequently deposit the resistive element on BeO, again for better heat conductivity.
So I would not dismantle a BeO containing device and would be careful cutting up old valves which may contain a variety of toxic substances as well as the Beryllium Copper hazard.
Those who worked in the manufacturers would know more.
Alwyn Seeds, Director
114 Beaufort Street,
SynOptika Ltd., Registered in England and Wales: No. 04606737
Registered Office: 114 Beaufort Street, London, SW3 6BU, United Kingdom.