It does look suspiciously like that Olympus. The front element assembly on the Mitakon does look a little narrower overall, which might make light placement a little easier.
If it's just a simple built in extension going from 4x to 4.5x, I wonder why it's so small? It looks like the front element hardly moves and that there would have been room for more extension.
3rd party reviews will be interesting.
Originally posted by Not a Number Canon's MP-E 65mm f/2.8 magnification range is from 1 to 5×, @ 5× the price. I'm not sure if it focuses to infinity.
There's no infinity focus on the MP-E, its minimum magnification is 1x. More expensive, but I'd consider it if it was in a Pentax mount. I agree that there's something to be said for not having to fanny about with bellows and all sorts of other adapters.