late 1920s, and units' semi-heraldic guidons were introduced in the early 1930s. In the late 1940s and early 1950s, the first unit's coat of arms were introduced, although in most cases these consisted of non-heraldic designs. In 1953, the Portuguese Institute of Heraldry proposed a system of rules to construct heraldically compliant coats of arms for the Army. Some units adopted coats of arms following these rules. In 1964 the Army finally started to experiment with the implementation of a regulation of heraldry and symbology, establishing strict heraldic compliance rules for the creation of coats of arms and heraldic flags for the units. A particular characteristic of these rules was the use of the heater shield in the coat of arms, instead of the traditional Portuguese shield with a round point proposed in the 1950s. Although an Army heraldic coronet was established, this was rarely used, with the coat of arms usually represented in a similar way to personal heraldry, with the shield topped by a helm and this by a crest. These regulations became official in 1969. The other branches of the Armed Forces followed the Army in implementing processes of heraldic regulation. In 1960, the Portuguese Air Force established a regulation of vexillology that also defined the unit's coat of arms to be inserted in their guidons. Most of these coats of arms consisted of non-heraldic designs. The Portuguese Navy established several regulations for the guidons of their units in the 1960s, but not rules for coats of arms. The Navy adopted its own heraldic regulation in 1972, similar to the Army regulation but preferring the use of round-bottom shields, and with the units' coats of arms being always represented topped by a naval coronet. The Air Force implemented its own heraldic regulation in 1985, based on the Army standards but with the unit's coat of arms always represented topped with an aeronautical coronet. Meanwhile, the Army changed its heraldry regulation in 1987, with deep changes in heraldic vexillology and also some changes in the heraldry itself. These changes were not adopted by the other branches, which makes the Army's heraldry, especially the vexillology, markedly different from those of the Navy and the Air Force. Army heraldry The present regulation of Army heraldry was established in 1987, replacing the regulation of 1969. The new regulation marked a deep change in the Army heraldic vexillology, that incidentally became substantially