It appears that Routens first of all was a bicycle shop, only secondly a frame builder. This is even more true today, with his son Jean-Paul Routens running the shop. I went there a couple of years ago, expecting something like the Singer shop, and was sorely disappointed. Most bikes there are labeled Routens, but it appears only few are built by Routens. Most others are standard Asian TIG-welded jobs. In all other respects, the shop resembles a big U.S. shop. Even standard French items like TA crank washers were not only not in stock, but they never even had heard of them. After much prodding, they dragged out an old Routens for me, similar to the one on e-bay, albeit from the 1950s. It had some nice features (Routens front derailleur), but generally was typical for a second-tier French randonneur. Not very exciting. (At least the 3-day ride from the Mediterranean to Grenoble was fabulous!)
Even today, Grenoble is full of Routens - every old lady riding to the store seems to ride one. Most look like repainted Motobecanes, which in fact they may be. The top-of-the-line Routens are not very common at all. I have seen very few very nice ones.
The nice ones all are fillet-brazed. The crossed-over seatstay attachment indeed was something of a trademark. The seatstay attachment of the bike on e-bay look somewhat like a women's bike I have that is very nice, very light, very well-done.
The twin-plate crown was used from about 1950 on, but not on all bikes. The above-mentioned women's bike has one. An early one I know doesn't. Some have the lower plate of the fork extended into a decorative little curl on the side of the fork - barely visible on Rebour drawing of the PBP-winning tandem in Vintage Bicycle Quarterly 2. It looks very neat, but I have seen only one bike with that feature.
The very best Routens appear to have used tubular racks, but most I've seen had racks made from steel rod (including the aforementioned women's bike and like the bike on E-Bay). To me, that lets them down somewhat. (Herse and Singer never used rod racks on their good bikes.)
The bike on e-bay is equipped with a BB for cottered cranks. If that is original, it indicates a lower-priced model. Not since the 1930s did randonneurs use cottered cranks on top-class bikes.
My feeling is that this is a second-tier Routens, built to a budget, but without a doubt built in Routens' shop. The frame workmanship looks very nice - Routens' fillet-brazing was as nice as one can get. It could be a very nice bike, but probably a bit heavier and less finely crafted than the best bikes of the era.
It probably dates from the 1960s, because before, they used Cyclo derailleurs. Routens also had his trademark front derailleur with very ingenious double-cable operation. A future VBQ will feature a wonderful Routens with all the special trimmings...
Hope this helps.
Jan Heine, Seattle