I believe you have a 1940`s or 50`s mid century modern ashtray !! The grooves were to rest the cigarettes and could be taken out for cleaning !! Remember smoking was a social event back then !! They are collectable !! Check ebay for prices !! Doesn`t have to be the same type ashtray !! The regular length cigarettes should fit nicely with the lit end over the deeper part !! They did not make 100`s back then !!