Yes, the Custom was offered for the last 15 years that Olds was in business. Initially it really was 'Custom'. A dealer would have a Custom kit of 3 different bells and 5 different leadpipes. You would try out the various combinations and then order your Custom version. Initially they would engrave 'your' custom combination on the bell but from what I've seen and what Alan Rouse agrees, I've only seen 37117 (37 bell? 117 leadpipe??).
All the info is here:
http://rouses.net/trumpet/olds66/customkit.htm and the horns are here:
http://rouses.net/trumpet/olds66/customtpt.htm and here:
http://rouses.net/trumpet/olds77/custombb.htm.
My experience is very poor silver plating and potential for valve problems in later years.