The Challenge: Identify items on Mozambique 1975 notes

It's been a while since I last posted a challenge, but I'm working on the Mozambique chapter of The Banknote Book and I came across the following unidentified items on the banknotes dated 1975.

Mozambique_BDM_10_M_1975.06.25_B6as_P121_A_0000000_f
Mozambique_BDM_20_M_1975.06.25_B7as_P122_A_0000000_f
Mozambique_BDM_50_M_1975.06.25_B8as_P123_A_0000000_f
Mozambique_BDM_100_M_1975.06.25_B9as_P124_A_0000000_f

All four of these circular items appear at right front on these notes. Does anyone know what they are, or what they are supposed to symbolize?

If you can precisely identify the name of these items—or have a lead which you think might be useful—please post a comment, preferably including a URL which links to evidence supporting your identification.

Also, according to the SCWPM, these notes (Pick 120-124) were unadopted designs, but I have a scan of a well-worn 100-metical note with normal serial numbers, indicating actual circulation. So, were they issued, and if so, when, and for how long?