First is part number. Also note that MatriKX is winding up their US production sites, all production being moved to India, the part number will become obsolete too.

Second part number though, I do not see it in their catalogue, either obsolete, or not MatriKX

Don't think that NSF = quality, unfortunately. We used to use Matrikx for Lite system, at some point production of Matrikx was moved to India. NSF remained, but quality dropped significantly. Pre-mature clogging, internal invisible cracks etc etc.

When in doubt, get original Omnipure. These are still US made and NSF 42. Company is super conservative, but it is not necessarily a bad thing. In many years that I used Omnipure it never let me down.

For micron, no need to go lower than 0.5. There are even very few companies that are able to make actual micron rating that is less than 0.5.

Where was this block made?
If you place ceramic after carbon, you will have clogged carbon and water that smells bad. Carbon is almost always the last stage. Nothing to do with micron rating.