It's a bn female the commons usually have more of an armor and it looks like solid plants and they usually have a darker appearance with brighter and more over spots.
Female bn plecos don't get bristles. However they can stick the sides of the mouth out the part that's by there gills if they feel threatened. I've had one that did that to me when I was trying to bag n tag it for shipping.
Some males are slow to develop bristles or slower than other's.
I had what I thought was a male/female long finned albino for nearly six month's before the slower developing male also began sprouting bristles.
Recenltly traded one of the males for three juveniles and hope to get a female.
Lost my old female that produced lot's of Fry when I removed a piece of wood that she refused to let go from.
Placed the wood in a bucket (no water), and noticed a stinky smell coming from the bucket a couple day's later.