Build number is 22G91
IPSW file:
https://updates.cdn-apple.com/2023S...11AD69/UniversalMac_13.5.2_22G91_Restore.ipsw
Full installer:
https://swcdn.apple.com/content/dow...m5sg2b4gpic7vz2i1s1n9n23/InstallAssistant.pkg
It's pretty obvious how to check the build number for ipsw files because it is in the link at the end and in the filename after you download it.
Not so obvious for the InstallAssistant.pkg's however. So
How to check the build number in InstallAssistant.pkg links
You can use this method to check the build number before installing it or even before downloading it.
Replace the last letter g with m at the end of the link and download the pkm file
Using this one as an example:
Open the pkm file with textedit and you will see
....version="22.6.91"......
The second number 0,1,2,3,... stand for A,B,C,D, etc. and so the 6 is a G therefore the build is 22G91
For betas there will be fourth number at the end, but this time 1,2,3, etc mean a,b,c, etc.
So taking the latest Sonoma beta as an example, you would see
....version="23.0.5337.1"...... in the pkm file
The second number 0 is A, the fourth number 1 is a and so the build is 23A5337a