How can I decide if I have the right (old) unlockable bootrom on an iPhone 3GS?

[iMore Question]

I am trying to decide if I have the right (old) unlockable bootrom on a 3GS and am getting conflicting results:

1. Serial number is [redacted], which would indicate week 33 of 2009 and so safe (old bootrom).
2. But, model is MC135LL and I have read that for old bootrom model starts with MB; MC is new bootrom. Is that correct?
3. iDetector says NEW bootrom.
4. f0recast doesn't say which bootrom, just that untethered jailbreak possible if old bootrom
5. Redsn0w 0.9.14b2 on the first screen doesn't say "Old BR" and I am told it should say that if it is old bootrom. And when I click Jailbreak the next screen says "New BR."
6. Redsn0w 0.9.14b3 also on the first screen doesn't say "old BR", but when I click Jailbreak on the next screen it does not say "New BR" either.
7. I put the phone into DFU mode and used Device Manager to check the Apple Mobile Device USB driver properties, on the details tab looked for Device Instance Path but there is no such option, so could not use that route at all to determine old vs new bootrom.

So, which one of these should I trust? I thought the serial number was the definitive way to tell (except in a certain grey area), but it is not consistent with what the other methods are saying and even the 2 versions of Reds0w don't give the same answer.

Thanks.

 

[Highrisedrifter]

I would say that from the list above, you have more answers that seem to say new bootrom. That being the case, I would always err on the side of caution and not JB your device in case it all goes horribly, horribly wrong.

I JB most of my current devices, so I am aware of the pitfalls that can arise and I just think that it's not worth it in your case.