Accutronics
I noticed the Accutronics (purchased by Belton) web site has some charts on it for decoding the alpha numeric designations. This might be helpful to you if you are still deciding what to do.
Some of the tanks are interchangable. Some have smaller tanks with shorter springs, while others of the same ohm ratings have longer or more springs.
Link to the type 4 accutronics tank specs.: http://http://www.accutronicsreverb.com/
Link to non-belton/accutronics upgrade, same tank: http://http://www.amplifiedparts.com...P-RMOD-4BB3C1B
Link to Tube Amp Doctor site for other replacements for the same tank: http://http://www.tubeampdoctor.com/...an-pid-276.htm
I'm sure you know, but output impedance and connector types are also things you may want to consider.
Evidently production has moved offshore and the quality of the new units is yet to be fully determined, but Accutronics was a very old US company with a work force that had developed a skill set, over the period of many years, that led to excellence in the production of the final product. Whether or not the new workers offshore have developed such skills is debatable.
I was told by a master amp tech that the new units are not close to being equal to the old units, but that was a couple years ago. R and D may have progressed very rapidly under the new ownership.
I'm not sure how much competition they have. More would obviously be better, but some other reverb tank mfg's are out there and you might be able to find one that sells retail. Since you are outside the US, Accutronics is probably readily available since it has Worldwide outlets.
Duffy Bolduc
South Williamsport, Pa.
"Now all the things that use to mean so much to me has got me old before my time." G. Allman, "Old Before My Time", Hittin' the Note.
Major changes to guitars and amps, to be updated soon.
Fiance - Supportive of musical art