Looking at the photos below, l would tend to group as

69/70 - 71/72
72/73-75/76 (V-neck)
76/77-77/78 (umbro badge)
78/79-79/80 (badge in the middle)


1969/70




1970-71



1971-72



1972-73 (v-neck)


1973-74


1974-75


1975-76



1976-77


1977-78



1978-79



1979-80