I had this exact same model a few months back. Bought it for $25. Sold it for $250:
Kitchen Aid Mixer 10 Speed Model K5A Beautiful Condition | eBay
Your appears to be in similar condition to mine but mine had the bowl and 3 attachments. The attachments sell for about $20 each. The bowl probably about the same. So, I would think you should be able to get $100 easy and probably $150 or more. Nice buy. Well played, sir!
BTW, we had a shot to buy another one of these (in the original box!) just this past weekend but we were a few minutes late. Some guy got to the yard sale a just before us and that was the first thing he grabbed. I don't know what he paid for it but, judging by the great prices we got on other things, he got it for cheap. Early bird, meet worm!
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