STM32F103
The STM32F103 processor is used on the Blue Pill STM32 Development Board.
Fakes and Clones
There are a number of "clones" of the STM32F103 available. Most of those are likely properly licensed Cortex-M3 cores with peripherals designed to match the original STM32 and most can be used as drop-in replacements with some "quirks".
Unfortunately there are also quite a lot of fake chips available:
Fake STM32F103 (possibly a HK32) from some random Blue Pill | Real STM32F103 from my own Green Pill board |
These are chips labelled STM32F103xxx but they are not.
PIN Count
Extra Flash
The STM32F103C8 is supposed to have 64kB of flash memory while the STM32F103CB have 128kB. Presumably, at some point, ST figured out that rather than producing two physically different chips it was more cost effective just to produce one and label it differently. For this reason, most (??? if not all) STM32F103C8 MCUs actually do have 128kB of flash even if they report 64kB.