This morning I received an email regarding this concertina from Vetiver, a person who signed as Michel. I was unable to respond to the email. But if Michel sees this, in answer to your query, the reeds are brass.
I'm selling my fully restored Wheatstone#7640 English 48 key treble concertina. Nickel flat topped pegs. Excelsior style brass touches. Embossed new 6 fold bellows, new pads, valves tuned to concert pitch. Dates from around 1860. With original wooden case and new gig bag. The concertina has been beautifully restored by Dave Elliott. Looking for £1300 but sensible offers considered.