Placing a production date on fleams can be very difficult.  No one factor can be relied upon to determine a pieces age.  The collector must use a combination of factors.  The general look of the item including blade and handle design (materials, presence of plating, shape, and construction), any makers marks, and engravings involving a date or ownership should all be considered.  Each of these items taken alone can give you an incorrect impression of the items age.  To understand some of these problems we should look at information on the history of cutlery, in particular as it pertains to the production of folding knives.  Much of this information can be found in Cutlery for the Table by Simon Moore. 
Folding knives began to return in popularity in the 17th century, having been absent for roughly a thousand years.  The return was led by the production of puzzle knives.  These tricky little pieces were produced initially in France and began gaining popularity in England around 1680.  These knives were made to both provide a ready piece of table wear and entertain fellow diners through the challenge of discovering the secret to opening and closing the pieces.  The complexity of the pieces and their impractical nature caused them to be quickly replaced with spring-back pocketknives in the third quarter of the 17th century.  The speed with which the diner could be ready to feast caused these knives to become all the rage.  These early items can be recognized by the powerful springs and the squared off design to the hinged tang that allowed the blades to be held in half and fully opened positions.  Other blade style changes in folding knives don’t really pertain to the folding knives we are researching with the exception of the development of the “nail nick” in the later 18th century.  You can already begin to see how this becomes a bit of a trick.

Aging fleams
The basic style of the fleam makes it difficult to get many clues as to the age of the piece.  The simplest designs are the non-folding pieces.  These solid pieces are almost always iron and often possess a very simple construction.  Simplicity of design should not however be a testament of an early piece.  Numerous cycles are present in the tool and tableware genres of cutlery that demonstrate variations in what is considered the pinnacle of craftsmanship.  Many times a pieces degree of decoration and complexity represents the skill level of the fabricator more than the period of construction.
Pieces from the mid 18th century begin to favor the folding designs.  Early pieces are found in iron, some with very decorative florid engraving on the scales.  Early pieces have very minimally worked metals or pieces shaped by very simple grinding techniques.  With the fact that very few design changes exist in the overall style of fleams, learning the progression in design and technique requires a process of linking forms to known makers.  The three fleams below demonstrate a style very typical for 18th and very early 19th century craftsmen.  The hammered flat brass and the simple chevron style to the blade basked is very common.  
  
Two fleams the one on the left is a very simple form and would defy the collector to date the piece since it could be an early form or simply made by a less skilled individual.  The piece on the right is a beautifully turned piece of iron with a lovely serpentine finial and cross-hatched decoration.  Made by the hand of a craftsman probably c.1650-1700.
Two fleams the one on the left is a very simple form and would defy the collector to date the piece since it could be an early form or simply made by a less skilled individual.  The piece on the right is a beautifully turned piece of iron with a lovely serpentine finial and cross-hatched decoration.  Made by the hand of a craftsman probably c.1650-1700.
Note the decorative patterning stamped on the hilt of this iron fleam.
A c. 1700 brass veterinary fleam marked: HOW.  This was made by the firm started by  Ephraim How of  Essex during the late 17th century.  His son John How inherited the firm and later turned the firm over to Savigny in 1720.
Brass fleam marked Coach no.2 1801 and Proctor on the case and an unusual stamp on the blade.  This was probably used for horses on a coach of fire-team.
Ornately enameled brass fleam probably c.1790-1810

The hinge rivet that attaches the blades to the tang is another good means of dating an item.  Eighteenth century items often have rivets that are very simple molded steel.  The later 18th century and early 19th century pieces begin to have a more decorative tiered rivet of concentric circles of brass