John;
Although at one time the Voit Duck Foot fin was the UDT/SEAL fin, I'm fairly certain that this is no longer the case. You can double check this but I believe they have moved on to one of the more traditional open heeled adjustable fins.
I dove for years with the original Duck Foot up until the early 80's when they became difficult if not impossible to find as VOIT sold their Diving line to MARES. The last pair I owned was actually a brown color and had a gum rubber foot pocket that made them a bit more comfortable to wear. VOIT also by the way had provided the Navy with a virtually indestructible regulator known as the MR12.
A shorter more flexible version of the Duck Foot was produced for the surfing industry as an alternative to the Churchill Swim Fin. Mostly used by body surfers and boogie boarders. Big Wave body surfers occasionally used the original UDT SCUBA fins in their place.
As I understand it, a company (?) has recently obtained the original molds for the UDT Duck Foot fin and they are back on the market. Based on the picture you originally posted, it looks as if that is what you got.
In one of your earl posts you said that you bought these to help you train for the military ? If I may, can I make a suggestion ? And since you didn't ask feel free to ignore it.
If you are preparing for a shot at BUDs, I would not be concerned with fin swimming at this stage of the game. There are a number of great
web sites available that can help you train for that experience. Just Google "training for BUDs". I would focus more on meeting and exceeding the minimum fitness standards for acceptance into BUDs. Should you be accepted, you'll have time to learn to swim with fins.
Good Luck
PS - I stand corrected. I guess that now they do in fact recomend pre-training swimming with fins. If you cannot find the USD Rocket Fins you can substitute SCUBA Pro Jet fins for training. Both fins require booties.