Audio Power Transistors - Buying in Bulk

Pop the can off the Multicomp and ON to compare the dies and bond wires. You will certainly find a huge quality gap.

Is that a side-by-side of the multicomp and the onsemi MJ15003/MJ15004?

No, mexican and chinese.

That's a horse of a different color, That's a fake part (the large distributors cannot usually supply fakes unless something goes seriously wrong). A very high percentage of semiconductors from China via AliExpress etc., are fake, but I've never seen a fake from Farnell/Newark (not saying it's never occurred for anyone, but it's exceedingly rare.

By 'fake' I mean that die could say be a deliberately lower-cost one (e.g. smaller and cannot support the same spec as the expected part), or is an old part (possibly faulty).

Do you have access to the Multicomp parts Shibaz? Could you open the metal case and post a pic? That would clear everything up once and for all. The specs sheet of the multicomp MJ15003/004 appear almost the same as the ONSemi part. Otherwise, I'll just have to place an order and open them up myself. Would Newark send me a couple samples for this experiment?

Unfortunately I don't have any : ( I've never received samples from Farnell/Newark, you could try phoning their sales desk, but I don't know if they can provide that or not. If you do manage it, it would be great if you could upload the photos of the internals here to help others too.

Why would you think it's a fake? Many parts sold at Farnell/Newark come from china. They usually have the same part numbers but different prefixes. Lots of different die designs are around for the same parts.

"Why would you think it's a fake?"

Because your photo was taken from a counterfeit transistor web-page that explains it in black-and-white:

As you can see from the red highlighted text, the purchaser was caught in a bait-and-switch. 

That's very different from the Multicomp part, which will, in all likelihood, meet the (limited) datasheet spec that it is supplied with. 

"Many parts sold at Farnell/Newark come from china."

Many fake parts come from China. But the OP is specifically discussing parts from a distributor that will have processes in place to prevent bait-and-switch.

"Why would you think it's a fake?"

Because your photo was taken from a counterfeit transistor web-page that explains it in black-and-white:

As you can see from the red highlighted text, the purchaser was caught in a bait-and-switch. 

That's very different from the Multicomp part, which will, in all likelihood, meet the (limited) datasheet spec that it is supplied with. 

"Many parts sold at Farnell/Newark come from china."

Many fake parts come from China. But the OP is specifically discussing parts from a distributor that will have processes in place to prevent bait-and-switch.

Fake because it was deliberately rebranded as Motorola.