Bridgestone MB-5 Question

George said:

I have a Bridgestone MB-6 that I bought new from Sheldon Brown many
years ago (i.e in 1993, I think).
I recently purchased a used MB-5. My understanding was that the
original MB-5 had thumb shifters and allow bars. The one I bought has
Rapid Fire shifters and black bars which, I assume, are steel. These -
especially the bars - look like original equipment.
Did Bridgestone change the specs on the MB-5 from year to year? The
fellow who sold me the bike says he thinks it's one of the last ones
made.
To reply directly to me, replace all 'z' with 'a' in email address.

'93 had Deore DX thumbshifters, '94 had STX Rapidfire.

Sheldon has the catalogs posted:
http://sheldonbrown.com/bridgestone/index.html

George said:

I have a Bridgestone MB-6 that I bought new from Sheldon Brown many
years ago (i.e in 1993, I think).
I recently purchased a used MB-5. My understanding was that the
original MB-5 had thumb shifters and allow bars. The one I bought has
Rapid Fire shifters and black bars which, I assume, are steel. These -
especially the bars - look like original equipment.
Did Bridgestone change the specs on the MB-5 from year to year? The
fellow who sold me the bike says he thinks it's one of the last ones
made.
To reply directly to me, replace all 'z' with 'a' in email address.

If not what wrong with up grading.