Very Spectacular Pens, and Superb Bakelite.
I cannot recall seeing Bakelite in Marbled Colours, that is in Australia.
Bakelite use to be used for just about everything, that was moulded.
It was a very poor conductor of Heat and Electricity, so was used for handles on Toasters, Ash Trays , Insulators, Ignition Rotors,etc.
Also was used to make Telephone bases, hand pieces,and Mantle Radio cabinets. Just to mention a few.
As mentioned by papaturner, it was virtually the first hard wearing, strong (though brittle) mouldable, Heat and Electricity resistant Plastic.
Brian.