I have a Sendra. Seems to be a well made lower. I don't know how to tell if is cast or forged but mine was supposedly made in the early '70's and is still in good tight shape. They got into some kind of trouble with the ATF and went out of business. I was told they were bought out by PWA but that is hearsay. Postban lowers have a circle machined in the side of the mag well. Anything without the circle is preban.

All I've seen have been forged.Well made lowers a real sleeper. Go to search as this was covered in depth a while back.

It might be a little out of date:
From the AR15.com Legal page:

www.ar15.com/articles/article.html?article=23
Serial Numbers:
Nesard
See "Sendra" below.
Sendra
Post-ban receivers have a circle milled into the side of the magwell. They were originally bead-blasted to a non-glare finish. All others are pre-ban. (This is unverified info…) Also, they used to be NESARD. Rumored to have been owned by Dick Drasen (currently M&A Parts) and produced lowers only out of Barrington, Illinois. No complete guns were sold (again, unverified info).

A friend of mine has a Sendra M16. All I can say is it seems to work. Looks like it's been around a while.