Oskar - does it look similar to the one in this link ?
http://www.gournetusa.com/forum/topic.asp?TOPIC_ID=208&SearchTerms=robust,ideal
I came across one similar to this a few years ago that was marked COSTO - it was very plain and in 12 gauge so I passed it by.
I have a COSTO Robust, also. Some where I read that since Manufrance was a big Mail Order House in France; some guns were trade marked COSTO so they could be retailed by other firms.
Who knows ? French Guns are a rule unto themselves, especially Manufrance guns.
