Well telling an HK94 from an MP5K is easy because they are different weapons (I think he means HK94 and MP5).
You can tell and HK94 from an MP5 because many movie armorers used to "chop and convert" civilian 16" barrel HK94s to resemble MP5s by cutting down the barrel and converting it to full auto.
Here's the images so you can see some of the differences I list:
This is a genuine Heckler & Koch MP5A3 with an S-E-F trigger group. Note the push pin in the lower reciever behind the magazine well, the paddle magazine release behind the magazine well, and the three lugs on the barrel.
This is a "chopped and converted" HK94. It has the 0-1 trigger group with a 2 added to convince the audience it has a full-auto selection. Note how it lacks the barrel lugs, the push pin lower reciever, and the paddle magazine release.
Now, I sense something negative in what you've been writing. Have I mis-read your writing or do you have an attitude?