If the ASE server was properly patched, then the install scripts, like installmaster and instmsgs.ebf, should have been applied when the binary was upgraded.
what you can do is check the date when the stored procedures in master have been created, e.g.
sp_help sp_dboption
The date of the creation of the stored proc is likely to be the last time the server was patched.
Note: it's possible that someone ran installmaster again sometime after the upgrade, but that should be an exception