(ET) 1971 Mower

Ok i have to say this is the hardest website i have ever tried to get on. My husband got one of these mowers given to him while he was on an excavating job and brought it home because he had never seen or heard of one before. I got on ebay and a lady out of Canada has an original 1971 ad for this mower and i e-mailed her and she doesn't know anything about them. My husband said that the guy told him that it used to have attachments, but all we have is the mower deck. (What attachments were there?) He also at first thought it took 4 6 volt batteries but after he worked on it the other day he found out it took 6, and he found somewhere around the battery compartment that it was a 1971, was that the only year they made these? The condition of the mower is really good, paint looks good, it just needs new tires. He thought about fixing it up and taking it to a local tractor/steam engine show that is in Rushville, IN every year and show it off and maybe sell it, but we kinda wanted to know what it would be worth or where all i can get info on it. If anyone has any info about this rare (at least it seems to be because we have talked to old people about it and most have never heard of it) mower we would welcome it. Thank You, Heather Levi (Indiana)