Even tho a Guinea Pullet's first few eggs can be odd shaped, it doesn't quite have the signature pointy end a typical Guinea egg has. As a general rule the normal Guinea egg shape is fat and round at the air cell end, narrow and pointy at the other end... but the shape can vary. The color and texture of the shell on your egg makes me think that is a Bantam egg tho.
If your Guineas are 15-16 wks or older they are definitely old enough to lay a few eggs before the season ends, they don't always wait until the first Spring after they are hatched to start laying their first eggs (but they are typically seasonal layers, Spring thru Fall).
That's not necessarily true... egg shape and shell color varies from Hen to Hen in Guineas, and not all Guinea eggs are speckled. I have A LOT of Guinea Hens (over 50 Hens in 15+ assorted colors/Pieds)... I collect eggs from them in a variety of different shades and hues of beige, but I only get speckled eggs from a few of my Hens.
Also, Guinea eggs aren't always short. I do get some short fat eggs, but I also have a few Hens that lay longer, narrower eggs. Even longer and narrower than Jcowgorl90's egg is (but they are still fat at the aircell end, pointy at the other end).
