[susan53]

To see if something is still current, try checking with a concordancer. Go to eg Lextutor. In this case,

1. Type observed of into the Keyword box, leaving the box to the left on "equals"
2. Go to the "Choose a corpus" box. Click on Brown if you want US English, BNC written/spoken if you want British English, or "All of the above" if you want a mix. (For this search choose "All of the above")
3. Click on "Get concordance". If a lot of examples come up, you know it's current and common. If only one or two come up, it's used currently, but is rare. If none come up it's probably not current English.

Try it. What happens in this instance?