Excellent questions, Weedwhacker! I bought the larger of the two kits on offer: 6 feet by 10 feet. I am in the process of laying everything out and can find no identifying information like a manufacturer's stamp in the aluminum. A thorough examination of the smaller cardboard boxes of bolts, clips and other fittings MAY reveal some vital information.
I've been looking at an assembly video of the Erromy 6x6 greenhouse and the extrusions look very similar to mine (the size and price don't match; I paid about $2,000 for the S&H kit in 1986!).
I even emailed Paul Hawken! A Jonathon Hawken replied saying the business has been sold several times over; try contacting Target. . .
Thank you for your note of welcome. It's neat--bordering on exciting--to receive a reply from Michigan!