The earliest Navajo squash blossoms had very little, if any, turquoise. Turquoise probably didn't begin to be put on Native American jewelry until around the 1890s.
The Navajo used turquoise usually in the form of nuggets or cabochons. Zuni silversmiths also began creating jewelry with small clusters of turquoise and coral, but that usually appeared more finer textured or daintier.
What you want to look for with the earliest antique or old pawn jewelry is that it has very little turquoise, and if turquoise is used, that it has very early bezels. The bezel is what attaches and holds the turquoise stone in place. Look for handmade bezels on early pieces versus something that looks more machined and commercially made.
Usage is another very important tool in determining age. You want to see beads that are very smooth that have been actually worn and used.
Often Navajo squash blossoms have old coinage on them and people tend to assume because they have these early coins dating from the 1910s or 1930s that it must be from the same timeframe as the coins are.
The reality is that's actually quite rare. Almost all of these Navajo squash blossoms were made in the 1960s and maybe 50s, and are a reproduction of an earlier type.
So, just because you have a Navajo squash that has early coinage on it does not mean that it's early - it just means the coins are - and that's a very important dating factor to be aware of.