My BB was the 28watt version (the normal 1962 Bluesbreaker) 2x12..same as your 90s version but a bit wider becasue from 2004 Marshall made the cabs to proper dimensions so you can fit in KT66 vales in it.
I had the 18watt version (1974x) it was very cool for a few gigs but mine blew up and its a LONG story...the early verions had a LOT of problems!!
The 90s RI did have the later cosmetics yes, i just consider the quality of the amp as it is though, ive heard a real 60's BB in RL and they sound really different anyway. My BB RI also was an early sample(mine is a '90 one), but i bought it used so i dont know if it had any issues. I do know the previous owner was really fussy about his amps so probably checked it thoroughly when he bought it. Maybe the best roadgear is the stuff that has worked hard for many years anyway thinking about it.
I have my Mules in a '76 Gibson custom, it has a maple neck with volute. This guitar makes them sound quite bright though, prilliant on the neck Mule but a bit too fusion like on the bridge if put trough my BB. When i compare my BB to yours, mine sounds more like your twin by the way, but at a higher volume the preamp and greenbacks come alive and then its totally different again, very nice noodleing stuff.
That CS '59 standard is just wonderfull! Love that top, the one i tried had a bit 'overdone' top which looked rather plastic, certainly not vintage IMO. Yours looks like it was just beamed up from 1959!
Heres the custom i put my mules in, the pickups are still the stock it came with though.
