Flench,
It's hard to tell the year of those old boxers as they didnt change much but I'd think it;s a 70's model,likely 75 to 78 however as I said it's hard to tell the year on a stock 1 never mind a custom!
I was looking around for an older BMW boxer and found a mint 75 for 3 grand,just been totally rebuilt! The wife ack shot me down right away though,told me I was too old for bikes and would either forget I was riding it or fall asleep while riding and she's not paying o bury me!!!!! 
YMMV.
morf..
Keep working on the wife! I've been with mine for 21 years this summer, and I just finally got her to give me the go ahead on a bike..... she gave in to racing, and eventually took up motorsports herself briefly with the Corvette Club, but was generally supportive of my racing habit.
Motorcycles were always her 110% No Frickin Way area..... my mom and dad both ride Harleys, and my dad had worn out 3 sets of tires on his Screaming Eagle Electra Glide, been to all 48 states and Canada on it, coast to coast twice. My wish was to be able to go along with him on a ride like that before he's too old to ride like that anymore (he's in his 70's) but the wife ack was skipping the wirbles and went straight to SAMs. No Way. Not Ever, she said. The day I showed up on a bike was the day she'd leave me. (I used to joke that I responded "now I know what it'll take to get rid of you!" But everone who knows her will tell you, of course I didn't actually
say that as I do in fact continue to convert oxygen into carbon dioxide.
)
So I dropped hints for a while, talked about dad's trips, looked at BMW airheads on ebay while she was around....... then one day she "out of the blue" says, 'you know, if you want a bike
that bad, I guess I'm OK with it, just keep the life insurance paid.'
I'm shopping for an early to mid 80's R100RS right now.
