The yellow anthers set off the dark colored petals, making for a pleasing flower.  I would likely choose this one as my favorite peony of the Black Pirate group.

It has pollen and is in the parentage of ‘Hephestos’ (Daphnis, 1977).

Cultivar: Thunderbolt
Year: 1948
Seedling No: 13014
Group: Black Pirate
Flower: Color: very dark crimson/maroon
Form: single, two rows of petals
Blooms: Week 5
Carpels: 4, green
Stigmas: bright dark pink
Sheath: dark red (“blackish-purple-Reath and Saunders)
Stamens: filaments dark red
Plant: Habit: wide rounded bush
Foliage color: medium green
Foliage form: slightly more narrow than most
Height: 34″ on 8 year plant
Recommendation: Recommended especially if you like dark colors
Availability: Few nurseries specializing in woody peonies