Help me identify MESA Boogie Box 4x12 Modell 4FL-R-SL

[DFGeneer]

Hello,

I see an ad on ebay for 4x12 Mesa cab model 4FL-R-SL. After googling it I couldn't find any info on that model.
So, I'm guessing FL stands for front loaded (it really looks like on the pic), R for rectifier series, SL for slant.
Am I right?

As well it's rated 280W, instead of the contemporal rectifier models with V30 rated to 240W. So, what speakers are in it?

And finally: is it closed back? Standard or traditional? Anyone has the same?

Thanks for the info!

 

[DFGeneer]

Anyone?