In reply to cuppatea:
> What would explain the lack of load rating?
Age, would be my guess. It was probably produced before there was an appropriate standard in place that specified that load ratings were to be displayed on the carabiner.
It was certainly produced before the current version of the standard for industrial carabiners, EN362:2004 (which obviously came into force in 2004). However I don't know anything about what, if any, previous standard there were.