Old Effigy vs Modified Effigy Halfpennys

In the image above, the left coin is an example of the Old Effigy type. The right one depicts a coin of the Modified Effigy type. Like the penny, one way to tell the difference is to look at the spacing between the dots of the colon (first set of circles on the images). The dots appear closer together on Old Effigy coins. Also the dots or teeth (denticles) of the border changed between types. The New Effigy coin has a much more pronounced set of dots (second circle on the images). They are larger and extend inward farther. The only date of overlap between Old and New Effigy is 1925.