Generally, the power is not marked on Fecker scopes.

JackHughs

Jack is right most Feckers are not marked. The only way that I know to really tell is to send it off and have it measured in a shop. 
What size is the objective bell? 
All the Feckers have the parallax adjustment in the center of the tube. It is the great advantage of Fecker scopes. You can keep your eye in the scope as you adjust.

40 Rod

Maybe this will answer some of your questions. My understanding the numbers on the parallax rings are reference point which you may record for different yard lines.
Kurt

Two more...
The copy of Strobel's book I have doesn't mention JW Feckers that are this short.

The following is from an article I wrote on vintage external adjustable scopes & discusses two techniques to determine the magnification (power).

One technique is based on the telescope "rule of thumb" formula that the exit pupil diameter is equal to the diameter of the objective lens divided by the power.  Put another way, the power is equal to the objective lens diameter divided by the exit pupil diameter.  The objective lens diameter is very easy to measure.  The diameter of the exit pupil is the size of the image projected on the pupil of your eye when looking through the scope.  Measuring the exit pupil is a little more complicated.  But with a little work and preparation it’s not too hard.  To make a good measurement the scope must to be held steady, not rigidly mounted, but held sufficiently steady to make a measurement of a focused spot which will be approximately 0.065” in diameter.

An easy way is to just lay the scope on a table.  Now align a bright light source, lamp for example, approximately 2 to 3 feet in front of the scope.  It must be in line with the scope and objective lens.  In other words, aim the scope directly at the lamp as if you were sighting it on the lamp.  If aligned properly the image of the light source should pass through the scope and form a small spot on a piece of paper held within inches of the eyepiece (ocular lens).  With the scope on the table and focused on a bright light, I taped a piece of paper on the back of a chair and slid it to within inches of the scope.  If the light source is too far away from the scope it may not supply sufficient light to illuminate the full spot or, if too bright, may flair out on the paper making it difficult to define and measure the spot edges.  Move the paper back and forth until the spot is focused to the smallest diameter.  Grab your vernier calipers and measure the spot diameter.  Divided the diameter of the objective lens by the spot diameter and you have the approximate power of your scope.

Another, possibly easier method for some is to use the method Chris (rgchristensen) mentioned.  I.e. the technique of looking at a small far away object with one unobstructed or "naked" eye while looking at the same object through the scope with the other eye.  Then, while superimposing both images over each other, estimate how many times the image seen by the naked eye will fit into the larger image seen through the scope.  As Chris mentioned, a brick wall is a excellent target.

Wayne