Identifying flatwound strings

[Dazed]

Have a set of mystery flatwounds on a bass I’m sure someone will recognise. 
 

Headstock end has red silks,

bridge has black silk

and enamel(?) ball ends in

red E

blue A

white D

red G

 

thanks

[sky]

those are rotosound 77s

[fretmeister]

Definitely Rotos!

[Dazed]

Thanks both. They sound fairly bright which surprised me, not sure how old they are. Do they take a while to break in? 

[fretmeister]

They do.

Steve Harris of Iron Maiden is a famous user for the brightness, but they get old and thuddy like John Deacon after a couple of weeks solid playing.