You can refer to this Wikipedia writeup on MAC Addresses. There is a section noting the frame where the identifier resides.
And yes, Hardware Manufacturer can be identified from the first 3 octet aka OUI
Sources: Wikipedia
What is an OUI then?
An OUI {Organizationally Unique Identifier} consists of a 24-bit number that uniquely identifies a vendor or manufacturer. The 24-bit numbers are purchased and assigned by the IEEE.
Wikipedia write-up on OUI If you want to jump straight to searching for Manufacturers based on brands. you could google it. Here are some of the links.