No wonder why I do not post many pictures anymore....photobucket has been kicking its own bucket many times over. Hard to get past the adds... aaaaah...
Finally got it to copy the image again.....
From top (C18) under the blob of glue. (yellow ceramic disc capacitor)
Next component down is the 82.5k 1% resistor (gray, red, green, red, brown) light tan colored resistor, could be metal film type.
followed by the 330k 5% (orange, orange, yellow, gold ) darker brown color (carbon comp as it appears)
and just below it is the 220k 5% (red, red, yellow, gold) darker brown color (carbon comp as it appears)
Note that the resistors are sitting on top of the reference designators so R218 (new) can barley be seen, part of the number is visible when looking at an angle).
The only thing on the top side of the PCB but doubt it is code for revision level as it may be a christening slogan is in the next image. Note the blue flame proof ceramic coated metal film resistor, you may have a dark brown carbon composition on the power tube board. It is one of the screen resistors that was replaced after originals split open (lots of phenolic burning smoke was the end result). So if you look inside your amp and do not see the same thing, do not worry, it is an image of the preamp board of a Mark V....
Birth date with partial view of SN
It does not take me all that much time to pull the chassis on this amp. I can do it with my eyes closed as I could not fit my hands inside the amp to get the tube shields back on when it was a head. Much easier to manage as a combo.
I have confirmed the previously stated changes have taken place at least implemented on or following July 2012. Considering how bright this amp can be, I can only imagine the 2009 version. Please pass the ear plugs, thank you.... Sill this amp is just great and it does get better with age and a bit of additional information what works (always best if it is an easy thing like a tube swap, that is golden...)