I had one I bought 13 years ago, when we had our first child. It had
an aluminum frame that had a hinged piece on the back so you could
stand the whole thing up to take baby in and out. It was a blue nylon
canvas thing - extremely tough. After it went through my three kids, I
gave it away, still in very good condition. It had the inner sling
seat you describe - the purpose of that is to be able to position baby
higher (i.e. a smaller baby or child will sit too low without it, and
a bigger kid needs to sit lower). It DID have a padded waist belt,
which is really important to keep the weight off your shoulders, and
I'm willing to bet money yours had one and its gone.

Mine was good to 40 lb in theory, but 40 lb of squirming, leg
swinging, head whacking kid was too much for this mom to cart too
often.

I loved that thing - very, very handy for grocery shopping, yard work,
house work so you have your hands free. It was better for me than a
sling, since baby was out of the way. Kids did pull my hair a lot
though, and my hubbies leather jacket had its collar thoroughly chewed
a few times.

I found one for sale on auction - sorry this isn't a good picture, but
this one is identical to the one I had - is this like the one you got?
You can see part of the waist belt at the bottom.
http://cgi.ebay.com/ws/eBayISAPI.dll...tem=2377517367

Mary G.
Mom of three (now 13, 10 and 6)