Hi,

I have also earned some 8051 from old harddisk drives (2 per drive). It was easy, since they are in sockets.

It is the cheapest way to start with the 8051.

But you can use it only as 8031 with external EPROM / Flash and it comsume more power than the today CMOS devices. So its not a fault, if it was very hot. They can also work at up to 12MHz only.
The today 89C51 devices should never be hot.


Yes, such devices should never be selled in production.
Also EPROM or Flash devices, which used for developing (reprogrammed several times), should never be selled.


Peter