How old is this Tandem Rear Steer Skip tooth ??
This looks like a prototype or maybe even a home-made version due to the way the horizontal cross tube for the second rider looks unevenly cut off just before reaching the first rider's seat post.
Dating will be a bit of a trick - the angles of the down-tubes don't match anything I can find on the net with a cursory search, but rear steer tandems were popular as far back as the 1890's in quite a few designs. Prices seemed to average around $150 USD. Many got recycled/refurbished in the 1930's and later, usually with upgraded seats and tires/wheels. The seat in the picture doesn't look more than 50 years old.
Brands names that I have come across are Colsen and Geneva.
The cranks remind me of pre-1940's bikes with the spindly crank arms, as opposed to tapered cranks that are more commonly seen today.
I would suggest looking closely at the frame, even the underside, for any marks that show names or numbers. Might be hard to do as the paint looks a lot newer than the bike and may have filled in the letter/number stamping on the frame, or any mounted/welded/riveted ID plates.
It's not too far off from the late 30's Colsen models, so I'm making an educated guess it is at least pre-World War 2.
update: looks like I found the exact same bike at this eBay link: http://goo.gl/yxirV8
added by Nul: Seller says: "looks as if it's been repainted at one time. the wheels and tires don't look right for this bike, although the rear wheel sprocket is skip tooth. seats are not original. one pedal is different from the rest. i do not know what kind it is, there is no badge. i did find a serial number on the bottom of the front pedal shaft housing. the number is in the photo, looks to be #46556. there are a few dents here and there. buy them when you see them!!"
Photos from auction (added so they're not lost when link disappears from ebay)
Auction closed on 30th June 2016 with a hammer price of $699.99 USD
Between wars seems most likely . Colson fits the structure , not a custom or prototype . 70 plus years old (plenty of time for alterations) . originaly had 28" wooden rims and single tube tires (very expensive to get now ) and was re-wheeled to make it rideable appears to be 27" likely done in the mid 70's earliest . Now 29er street tires would fill the fenders well . The "hacked up" bottom bracket was frugality at the factory >make it with what we have here< common to low volume cycles then. Great find , enjoy the ride .
*****Clearly a 1939 or earlier era bike, (never judge a bike by it's tires, or crummy seats) clearly painted by a 7th grader. Even the serial number look VGT, skip tooth and other accessories tell me it's pushing 80 years old. Someone needs to strip it, get proper wheels, tires, seats, and make it presentable.***