Below is the text from the seller of the amp.

"Overtone Special Reverb built using Ceriatone chassis and panels.

This is the ‘Skyliner EQ’ version of the OTS which gives a smooth overdrive tone varying from slight crunch to hi-gain and everything in between.
Some modifications to the circuitry as follows:
Circuit upgraded to include Fender AB763 type reverb.
The pre O/D gain control has been extended to the front panel and takes the position of the FET input socket (FET input removed). This allows matching of your guitar gain without dismantling the amplifier.
Reverb ‘Dwell’ and level controls fitted on rear panel.
Transformers by Hammond and Marshall.
Presence control has been converted to overdrive channel tone cut control.
When mid boost or O/D channel are engaged the reverb drive is automatically reduced to avoid overload.
Recently serviced with new output valves (JJ 6L6)

In combo cabinet with Celestion G12-65 Heritage speaker.
Supplied with custom cover and 3 switch footswitch (Reverb, Overdrive and Preamp Boost)"

Hey I know he uses multiple amps together and eventually would like to get a Marshall, it's just the overtone is going cheap.

I do like other tones other than bonamassa, like John mayers tone.

I was thinking that the overtone with a tube screamer would be a good start. Seen as it says that this is a modded version and get good gain.

Hey guys thanks for chipping in with the help, looks like im after a jubilee so or clone first, looking to preferably buy second hand, if ye know of anyone selling either one.

I know and it's a great price it's just, shipping and 26 percent vat and customs then in Ireland is what gets me.

I went this way for bonamassa ie D style amp and mashally pedal. It worked out better imho cause its easier to replicate a good marshall tone with a pedal, much harder to get D style bloom from a pedal. And if you do it expensive ie Zen or Dumkudo or Ethos running up to several hundred bucks vs marshal clone pedals at $150 ish.

my 2c

oh and you wont get close to Mayer with a Marshall

the only little problem with a bluesmaster idea is that at the end of the day Bonamassa's tone is not a processed as you think amd his dumble tone is from a HRM variant called a Van Weelden. True he does use pedals but his base lead tone is a mix of the jubilee and the van weeldens (dumble clones). From what I gather the van weelden is a HRM dumble and not a bluesmaster variant. He uses the dumble clone to layer over the top of the jubilee for big leads, and its really hard to control that amount of gain and do it well - kudos to Joe!