OK, since originally posting have done a little research on sources for paracord and am wondering which is better, the 550 Type III or the 5040 Type III?

I usually buy mil-spec 500' rolls on Ebay from the cheapest source.

The military's official specifications for "550 cord" (which is a generic term these days) is 5040 with (H) being the latest revision. There's a "Commercial" version of "550 cord" out there, but most places don't attempt to pass it off as mil-spec.

As I alluded in my post, "550 cord" is largely a generic term these days. The best practice (if your cord usage is critical) is to buy from reputable sources. The good stuff will be designated Type III, have 7, 8 or 9 twisted core strands, and each of those strands will be of twisted 3 strand construction, as well. The stretch/elongation rating will be at least 30%.

If you're buying cord that was actually produced under a government contract, one of the inner strands will "color marked". The outer sheath color means nothing in terms of quality or specification and there are a number of suppliers selling quality cord that otherwise meets most of the mil-spec standards.

Update: Ended up ordering from Paracord Planet. Excellent customer service-they answered all my technical questions and I had my order in two days with free shipping.