Garter and buckle raf badge

[PROF DR IVAN MILOVIC]

The badge of the Royal Air Force features an eagle on a circlet which is surmounted by a crown. It was based on a design by a tailor at Gieves Ltd of Savile Row. It was first used in August 1918 and the original circlet showed a garter and buckle. The present plain circlet dates from1923. (Being noted that the garter and buckle were heraldically incorrect). This information does not help much in dating RAF militaria because it seems that garter and buckle version was indiscriminately used after 1923. The same confusion is with the eagle facing left and then right.
Can anybody add more detailed information in dating RAF items?

[oldlincolnian]

the matter of the RFC and RAF eagle's facing direction is simple and clear. On official heraldry the eagle should be facing to ITS left, or to the right as the viewer sees it. Eagles do exist which show the bird facing the other way. These include shoulder eagles and arm eagles. The governing rule is that symmetry matters and as such any eagle worn on the side, on sleeves or shoulders, should always be facing to the rear of the wearer.