Hi T-Mar, from what I understand the Motobecane serial number system is a touch bonkers. The serial on this bike is on a seriously faded sticker mounted to a chainstay. This is what I could decipher:

top 6 digit code: 021 633
bottom code: G6490175

These bikes are apparently a very nice ride but I bought it purely as a standby or "disposable" bike, and ideally as a trader for a hardtail mountain bike frame in my size. For a near BOTL bike it is very nice. I can only imagine how nice the upper echelons of this series is. The Huret & Maillard parts don't seem to hold up to well to weathering, but then again I have no idea how this bike was stored.

Here are the other pictures of the components: What's so special about French bikes?