5N and poor man's macro

I think this is a nice example of what one can get with cheap extension tubes...
Maybe the focus area is not OK (shallow DOF!), but I am amazed at the details...

This is a macro of a 10 brazilian "reais" bill (R$10.00). For those who don't know here's the bill: http://www.bcb.gov.br/htms/mecir/seguranca/seg010.asp?idpai=REALSEGUR

taken with nikkor 50mm 1.8 (from the 80's I think) and an extension tube very much like this one http://www.ebay.com/itm/Macro-Extension-Tube-Ring-For-Nikon-D5000-D3100-D90-D300-D700-D7000-D5100-Camera-/350550904325?pt=LH_DefaultDomain_0&hash=item519e764e05#ht_3290wt_682

Of course this is not for the pros or "serious hobbyst", just for you who love to have a little fun with macros..