AMIBIOS 2.2x (name assumed) is a version of AMIBIOS released in 1986. It was first developed by Access Methods and then by American Megatrends (after they acquired the AMIBIOS source code). This version is also mentioned in the POST code list of the unofficial MR BIOS website, which is where the naming of this version is assumed from.
POST screen
The POST screen is almost completely different from the (likely earlier) one seen on Rev-X2-03 (AMIBIOS 2.03) and also on the later AMI Plus BIOS. Assuming Rev-X2-03 was released before it, visible changes on the AMIBIOS 2.2x POST screen would be the removal of extra spacing in the "(CPU)-BIOS" text at the top and the inclusion of another AMI copyright right next to it. The new copyright also includes the copyright year(s).
A quirk with the new copyright is the inclusion of multiple years, with the first often indicating 1985. Although this may indicate AMIBIOS 2.2x was released in 1985 instead, that is likely for the year of the foundation of Access Methods instead.
The memory test counter has also been changed. The new counter now tests the total memory, rather than testing base and expanded memory separately.
String
AMIBIOS 2.2x is also the earliest known version of AMIBIOS to include a proper BIOS string in the POST screen. This early string is in the MMMM-SSSSSS format (MMMM for manufacturer code and SSSSSS for the BIOS revision release date). According to The BIOS Companion, later cores should include a newer string format that is also seen on AMI Plus BIOS. However a known release from January 31, 1989 (013189 in string), which despite being released quite late, lacks it. The string is also referred to as a "Reference number" with some revisions of this version.
String format:
MMMM: Manufacturer/OEM identification code, SSSSSS: BIOS subcore release date
MMMM-SSSSSS
Example string: 1406-061286
This string is for a 06/12/86 (June 12, 1986; date is in American format) dated revision of AMIBIOS 2.2x for Flying Triumph Co. Ltd. ("1406").
For a list of manufacturer identification codes, refer to the BIOS string codes list on SoftHistory Wiki here.