MSefi.com read only forum (Jan.15,2018)

I'm building yet another MS2 V3 , and notice the device inside the bag labelled BIP373 IGBT is actually marked 301,1,5 64971,1 1023/03.

Should I be worried - or is this just a code Bosch used when supplying a maker who wanted their own part number?

Those numbers sound pretty much correct as long as it's got the Bosch logo. Unlike some manufacturers, Bosch doesn't seem to write their basic part number on semiconductor parts.