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As mentioned above, there are several different versions of this mechanism. For example, [[Waterman]], in order to circumvent [[Sheaffer]]'s patent, introduced, based on Barnes's patent, a lever pivoted directly inside a metal cage that contained the entire mechanism. This in turn was fixed with fins to the pen, using as housing a special slit created in the barrel side.

As mentioned above, there are several different versions of this mechanism. For example, [[Waterman]], in order to circumvent [[Sheaffer]]'s patent, introduced, based on Barnes's patent, a lever pivoted directly inside a metal cage that contained the entire mechanism. This in turn was fixed with fins to the pen, using as housing a special slit created in the barrel side.

A more efficient system, later used by other producers including [[Sheaffer]] itself, requires the lever to be held in place by a metal ring through it. This is inserted inside the pen and maintained in position by means of a special groove, made internally on the barrel in correspondence with the lateral opening from which the lever itself is housed. This system has the considerable advantage of greater mechanical strength, since it does not require drilling holes for the pin in the material of the barrel, which in ebonite pens was often quite fragile.  

A more efficient system, later used by other producers including [[Sheaffer]] itself, requires the lever to be held in place by a metal ring through it. This is inserted inside the pen and maintained in position by means of a special groove, made internally on the barrel in correspondence with the lateral opening from which the lever itself is housed. This system has the considerable advantage of greater mechanical strength, since it does not require drilling holes for the pin in the material of the barrel, which in ebonite pens was often quite fragile.

Other variations of the system concern the way in which the lever exerts pressure on the sac: for example the [[Eversharp]] did not use a flexible bar but a flat bar with the sides folded like a "U", anchored on a hook on the bottom of the pen. The lever was equipped on the external end with two tips that went to fit in the rail obtained from the folding of the bar, so as to raise it to the rest position after filling, furthermore to keep the lever locked in the rest position, it was equipped with small protrusions that went to fit into special recesses created in the housing slit.

Other variations of the system concern the way in which the lever exerts pressure on the sac: for example the [[Eversharp]] did not use a flexible bar but a flat bar with the sides folded like a "U", anchored on a hook on the bottom of the pen. The lever was equipped on the external end with two tips that went to fit in the rail obtained from the folding of the bar, so as to raise it to the rest position after filling, furthermore to keep the lever locked in the rest position, it was equipped with small protrusions that went to fit into special recesses created in the housing slit.