Determining Database DBID - Database not open

[oracle@orcl ~]$ strings /u02/oradata/orcl/sysaux01.dbf | grep DB_ID
DB_ID 941873125

or

[oracle@orcl ~]$ strings /bkp/orcl/backupset/df_ORCL_11_1_787935734.dbf | grep MAXVALUE
941982635, MAXVALUE,