This used Weber Minimass 50w Attenuator is in Excellent condition with modest signs of handling and use.  Despite its name, be aware that the Minimass 50 is designed for use with 35 watt amplifiers and lower.  

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If you have a Tweed Bassman or Super Reverb, you should get the Mass 100.  The Mass 100 has the proper power handling as well as the 2Ω setting