After the death of Prince Albert Queen Victoria opened Parliament only 6 times.
5 of those occasions were after she had the small diamond crown made in 1870.
I believe that, on all of those occasions she wore the small diamond crown. In the earlier years press reports specifically stated that she wore a small diamond crown. Later, the reports mentioned only a crown but specifically said that it surmounted her white widow's veil, which indicates she was wearing her small crown.