From this site
One of my favorite lower beach hunting situations is running across hard packed sand, especially on beaches known to produce older finds, like these Spanish military buckles from the 1700s.
These buckles were recovered on a Treasure Coast several years ago, a month apart at the same site.
On both occasions it was during a full moon low tide that exposed a hard packed lower beach with a mix of sand and shell.
My guess is the buckles were trapped in that hard packed layer for a long time, over time the top layer of loose sand was washed away from the area and I happened to be in the right place at the right time.
Although I knew the area could hold something good, it took a pulse induction metal detector with a large search coil to get to the first buckle.
Check out the file marks on the hand made buckle and the intact closing pin on the encrusted buckle.
I recovered the second buckle on the next full moon using a VLF metal detector with a large search coil.
The day I found the first buckle I was using a VLF metal detector with a 10 inch search coil, but after not detecting any targets I grabbed my PI metal detector.
I could have easily moved on using the VLF, but luckily I took along my PI which is exactly why I always like to own a pulse, even though it spends a lot of time in the closet.
If you are like me and love searching for old coins and artifacts at the beach, you need to invest in either a large search coil for your VLF or add a pulse induction metal detector to your beach hunting arsenal.
You may have heard beach hunters referring to low spots on the beach, and how they are often the best areas to search.
Combine low areas on the beach and hard packed sand and it is double the fun, as long as you have the equipment to detect deep targets.
Also make sure you have a good strong long handled scoop capable of digging targets out of dense layers of mud, clay, shell or sand.
No sense in detecting deep targets and wasting your time wigging a coffee can size aluminum scoop from side to side trying to dig targets out.
When a great hard packed lower beach hunting situation comes along, make the most of the treasure hunting window.