Hi Jason,
Speedmaster101 has a page on this model here:
http://speedmaster101.com/145-012/
The assessment guide might also help get you oriented on some of the key terms and concepts people use when discussing vintage speedmasters.
http://speedmaster101.com/assessment-guide-2/
You are correct that the bracelet is wrong. It's a much later, modern bracelet. Period correct ones - like 1039 or 1171 - do appear for sale, but they're usually not cheap. The bracelet reference should be stamped into the clasp; yours is probably 1498 or 1998.
Here's a good reference chart on bracelets:
http://issuu.com/mstanga/docs/tab_bracciali_omega_ultima.xls
You have a nice watch there, and it's even nicer that it came from your brother. It has a few issues, but it also has a lot going for it. Get to know the watch and enjoy it.
Edit: oh, and nice DO90 bezel!
Click to expand...