Are you suggesting that Lange has sold more than their limitation? Thus, if Lange promised the limitation of 100 pieces, do you suspect Lange sold more than 100 pieces? If you suspect this has happened, can you give us a little more details as to why you think this and why you have made this statement casting a suspicion?
I'm not biased for you/Lange nor against you/Lange. I'm just curious why you think Lange has made more than the limitation on this specific piece. I've never heard anyone making such a statement before against Lange. But Lange is hardly a perfect company when it comes to certain things (early 1815/Saxonia models for instance were not fully finished for instance, an expose was made). Lange does often number their limited editions, so it'd be definitely funny if two #38s were in the same room!
To answer your question in the typical scenario, it is standard practice for many brands to make a few "extra" pieces that are prototypes. These pieces are generally never sold, although mistakes do happen. Big companies often destroy the pieces, but sometimes the person tasked with destroying them may keep them! Thus, companies have a policy that two (or more) employees have to be present to witness the piece being destroyed. Of course, the policy isn't always followed. These prototypes will eventually get "caught" if these watches are returned for service, the serial number may be logged as a prototype, and the company may refuse to service the watch. When a company says your watch is "One of 200 watches" then I understand your suspicion; but when a company like Lange actually engraves on the case your watch is #38/100, that shows confidence - because if there are two watches with #38, and the owners find each other on the internet, that would be a PR DISASTER for Lange.
And to answer your question in the other scenario, there are also a few brands that make MANY MORE than the limitation allows. For example. Ferrari's limited edition cars are known to have somewhat badly kept secret overrun production cars that are sold to customers!!! For example, there was a limited edition Ferrari Enzo V12 mid engine car. Ferrari claimed they only made 399 of these cars. Then they made one for a charity. So that math brings it up to 400. However, well over 400 VIN numbers exist on these cars (prototypes get VINs too, but the number exceeds registered prototypes) in Ferrari's service computer. Furthermore, let's say some owner has an accident and the car is totaled. The VIN Is resurrected after an accident. Thus, some car collectors say, Ferrari has built around 500 customer Enzos (not prototypes). However, collectors are not "experts" and thus, in a court room, their testimony isn't valid without evidence - the evidence is difficult to obtain conclusively.
You would imagine a lawsuit against Ferrari for false advertising. In many countries, as an original customer at a Ferrari dealer, you can sue Ferrari for contract breach, torts, bad faith, etc. However, in most countries, you would have to prove that Ferrari's bad actions cost you money. In the case of the Ferrari Enzo, the car went up in value even though they made extra vehicles. So you didn't experience a direct financial loss. Thus, this practice is kind of an open secret among Ferrari owners - this happens, one doesn't complain, as long as everyone is making money.