smc pentax close-up t9-2x: how know this?

Who know this close up and his value and quality?

Do you mean the T6-2X teleconverter?

I've just bought one for £33.00 and have yet to test it out properly. I have always wondered if the marque converters were better than the indepenent ones and there's only one way to find out!

Specific marque converters for high quality telephoto lenses are no doubt superb - for example, the range of Leica converters for their very long lenses.

The Pentax T9-2X appears to be a multi-element close-up lens that can attach to the front of a ring flash. When used in conjunction with a Pentax 100mm Macro will give 2:1.
If you do an internet search on Pentax T9-2X, open up the reference on DPReview and you will see some information and image examples.