Yes, the Musicmaster and Duo Sonic II type bridges are "top loaders" and the strings anchor at the back of the bridge. I actually greatly prefer the design compared to a Mustang's tremolo; it's far more stable in terms of tuning. There is also a six saddle (fully adjustable) version of the "Musicmaster" type bridge that was made more recently for the Toronado - those do have a string through the body design, but are otherwise similar looking.
When we had the guitar down at the Fender Custom Shop doing the routing for the second pickup, we misplaced the bridge, so I ended up buying a second one via ebay. Dennis called me up a few days ago and told me he'd found the misplaced bridge, so now I have a spare one. I also have two spare necks, so I may just have to find another body somewhere and build another guitar.
I did make one slight improvement to the basic bridge - I replaced the three stock saddles with brass "compensated" saddles. They improve the guitar's intonation quite a bit.
Here's a pic of the '75 Duo Sonic and my '71 Mustang that was taken prior to me starting the refinishing on the Duo Sonic. I don't think the pic is detailed enough to really see the bridge and saddles very well...
Here's a picture of my Telecaster that shows the saddles a lot more clearly. I have the exact same type of saddles on the Duo Sonic's bridge now:
And finally, one last picture of the Duo Sonic's body now that I've applied the final coats of clear - it's getting shiny! Now I just have to wait until the paint fully dries and cures before I can start the final sanding and polishing...
