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"It is a 2601 model and features the Arp 4072 filter. It is a really lovely sounding machine. The modules inside are not encapsulated, making it very easy to service. This is one of the more desirable 2600s in that along with not having encapsulated modules, Arp used better jacks on this model, that were hand-wired to the circuit boards. All slider caps are present, as is the original lid for the 2600 console and the keyboard. The keyboard is a 3604-P version, and works well. All keys trigger just fine. The keys are all a little stiff, but everything seems to work just fine (I mostly use the 2600 with step sequencers)."