What is this??

I bought this at one of my favourite charity shops today.

  

It's a spongey sort of pad, covered in what looks like calico, attached to a circular wooden base.

 

There are 3 feet on the bottom of the base (on the base of the base, as it were).

 

In the centre of the three feet is a screw...

 

...which is completely removable...

 

Enabling the whole lot to separate into 3 pieces.

What is it???

I gather it has applications of an embroidery/needlework nature, but how?  And what is it called?  I've been searching most of the afternoon on t'interwebs, but all to no avail.

Answers on a postcard please.  Oh - keen eyes will see it cost me the princely sum of £2.50 - do you think this is a bargain?  I'm fairly sure it is, even if it's an outrageously large pincushion, or a ridiculously small footstool...

I should add too that it's 25cm across, so that should give you some idea of the size (quite apart from my hand, which isn't large, but then again, isn't quite the size of a child's).