I suppose you could also place a glass or cup on it.

Writing Chair Manufacturers,Exporters,Suppliers,Traders,Companies,Factories at Alibaba.com, the world's largest ... Folding chair with folding writing board ...www.alibaba.com/showroom/Writing_Chair.html - 102k

Auditorium Seating Chair With Writing Pad products are sourced by buyer ... Invoice) for the following Auditorium / Cinema Seating Chair with writing Pad. ...alibaba.com/.../Buy_Auditorium_Seating_Chair_With_Writing_Pad.html

school chair with writing arm, usa, 1930 ca. school chair with writing arm by franco albini, 1950 ca. ... congress chair with writing tablet, usa 1975 ca. ...

The Writing armchair has an antique and a modern form. In its antique form it is known as a writing armchair in the United States and as a tablet armchair in the United Kingdom. It is more often than not a Windsor style armchair with a circular or oval pad or tablet replacing the right arm or mounted above it. Many versions have a drawer built under the pad, to hold writing implements.

ttp://www.tradeindia.com/Exporters_Suppliers/Exporter2049.26003/C...

http://www.usmarkerboard.com/dynamic/view_product.php?id=138...

There are plenty of refs.

I used to hate those things on the old wooden chairs. They were always on the right side and I'm left handed.

http://www.classroomfurniture.com/ - flashes up a variety of pics.

And if you click on a picture at top of this page, you get chair-desk too: http://www.amdesk.com/