There is no such thing as “semi-binary.” The only “place” I've seen terms like “semi” or “broken” thrown liberally at inconsequential serial numbers are either on “planet eBay” or on social media. Both virtual locations are notorious for extreme hyperbole (like “broken ladders”) & I would avoid being sucked into that virtual vortex (of virtual collector jargon that really doesn't exist at real coin shows). If you meet a dealer & ask him how much your “semi-binary” serial # is worth, he'd laugh. Think of special serial numbers like errors- they have to be dramatic & a number you (& most collectors) are going to say, “I want that!”
Your note would have to have a serial number of 2992992 (2 digit radar) or 29292929 (2 digit repeater). The last 2 digits (79) ruin the pattern on your $20 & that is often the case (the reason real special serial numbers are tough to find). It's a spender in EF condition (or you could try to swap it). I have found radars & repeaters (of today's series) that I put back into circulation b/c I know most collectors won't give me any premium above FV (Face Value).
There are 2 digit serial numbers (like 2992929) which are the lowest priority for most special serial number collectors. Very few might seek these but they're from UNC runs & are in UNC condition. Most special serial number collectors seek AU to Gem UNC exclusively. That means no EF or lower (unless eye popping solid radars or 2 digit radars). Every collector may have their exceptions to this rule but that's why collecting is interesting. Typically, notes have to be from older series to draw much interest IMO.
Hope that helps!
