If you post pic and tag me so I get alerted I can identify for you

 

Geissele HK MR Trigger - Place to look, the #2 circled above the G on the Trigger

Geissele CSASS Trigger - Where the # is imprinted it is instead milled out / lightened on the CSASS

 

I'm also interested in details. I cannot find nor think of a single detail that is different between the two from a function standpoint.

 

The only visible difference is what I mention above and each CSASS trigger was made per HK specifications. Each one has a Geissele Inspection Sheet where they were signed off on by an individual and actual pull weights written down.
First Stage 1-9-2.9 lbs
Second Stage 1.1-2.1 lbs
Total Weight 3.5-4.5lbs.

Are we able to purchase the CSASS trigger? I was not able to find that model number anywhere.

The person who purchased these 9 pictured resold them to market but who knows actually how many more are out there.

 

Are we able to purchase the CSASS trigger? I was not able to find that model number anywhere.

 

No, you cannot. The closest you can get is the HK417 trigger from them, which I highly encourage.

 

Does the CSASS trigger retain the safety function with the hammer forward?

 

No. Neither Geissele trigger retains the function.