British 1972 Proof Coins Not In "Official" Sets

A question for the early decimal experts...

I bought a British 1972 Proof Set at my local coin club auction last Friday. Looks nice and neat enough, only... it turns out it's not an official Royal Mint proof set. Here's the box it came in (I removed the coins and put them in 2x2s; I don't think this box is an optimal means of preservation):




Firstly, my case doesn't "look" official. Note the absence of The Royal Mint logo, either on the outside or inside of the case. There's also no square Royal Mint medal as is normally included in a proof set, nor is there space provided for one. The workmanship is pretty shoddy, too - the black foam lining pops right out if you tip it upside down, and some of the coins were a bit "loose" sitting inside there.

Secondly, all the pics I could find of a 1972 Proof Sets don't look anything like this. They look like this, wrapped in a cardboard folder as normal for proof sets of this time period.

Now, this is definitely a set of 1972 coins, and all the coins are definitely proofs. Besides the evidence of what would once have been a lovely mirror finish, they have to be proof coins; no British coins (except for the 25p crown) were issued for circulation that year. Only proof coins were made with the date 1972. So it's not a case of something similar to this thread, because there are no circulation coins somebody can insert in as pretend proofs.

Now, Krause lists the mintage for all 1972 proof coins at 150,000. But it also lists the mintage for the Proof Sets themselves at 150,000. So logically, every single one of those 1972 proof coins would have been originally issued in a Royal Mint Proof Set case.

So, my question is... how did my coins end up in this shabby "wannabe proof set" case? I'm a coin collector, not a pretty packaging collector, so it doesn't really bother me that a set was broken up, but I'm still curious what the story is here.

Why would anyone bust open a perfectly good proof set just to repackage the coins in an inferior case? Where did my medal go? I want my mint medal! Did some coin dealer really think that their style of packaging was so superior to what The Royal Mint was using that switching them out would be worth the expense? Or are Krause's mintage figures as bogus as this case?