The circle/dot symbol is very old and is shared by many diverse cultures and geographic regions....although the meaning for each may be slightly different.......... I have seen this marking on African pieces as well as Arabic, Indian, Afghan etc.
"...........CIRCUMPUNCT - CIRCLE with DOT (BINDU) in the center: ~The sun, a sun god (called Ra in Egypt), ~Gold (as in alchemy), ~An (unbiblical) archangel (Kabbalah), ~emotional restraint (Freemasons), ~ The creative spark of divine consciousness within people linking everyone to the creative mind of a universal "god" thus making each persona "co-creator" (astrology). ~In the complex symbolic system of Hinduism and Buddhism, the bindu (dot) represents the male force. Together, the circle and the bindu symbolize the spiritual merging of male and female forces. .........."
".........Circle with a Dot or Circumpunct
The circle with a dot in the center is perhaps one of the simplest and most incredible of symbols. The circumpunct has been used for an incredibly long time. The symbol once was a representation of the sun, and as such as been the symbol to represent the Archangel Michael. The circumpunct is also the alchemical symbol for gold.
Perhaps the most profound meaning for the circle with a dot in it is that of God. I had a professor once who had asked the class to draw the best representation of God. There were some students who drew Christ, others an old man in a chair, and then there were some that drew the Hindu gods. In the end all he did was draw a circle on the board with a dot in the center.
“This is God, the circumpunct is perhaps the most perfect symbol to represent God. The circle,” His finger traced the circle on the board. “represents the all encompassing power and infinite limitlessness of God. While the dot,” He pointed to the center of the circle “Represents our place within God, we are part of God. The circumpunct represents the perfect union of the divine and the created. The dot can represent anything within the omnipotent divinity of God.” He walked around the room in a circle then stood in the center. “Or it can also represent the self. The circle can mean the body, or the conscious self, while the dot can represent our subconscious or super-conscious.”
The circumpunct is indeed profound with its meaning ranging from an explanation of deity, to an explanation of the self. These two points in addition to its ancient meaning of the sun earn the circumpunct the rank of most symbolic of all symbols............."
"......Although not as dominate as the emblem of a cross, the ancient symbol of a circle with a dot in the center , can be found in almost every culture on earth...."
"..........The Egyptian eye of Horus (the Wedjat) and Turkish nazar or göz (a blue circle with a dot in the middle) all are symbolic eyes used to deflect ‘the evil eye’. A blue protective eye can also be found in on some forms of the Hamsa hand, an apotropaic hand-shaped amulet used against the evil eye found in the Middle East. In Jewish culture, the Hamsa is called the Hand of Miriam; in Muslim culture, the Hand of Fatima......."
As to Colin's knife...there is still a possibility that this is an African 'copy' of a colonial knife
Below is a picture of a Sumerian Alabaster bowl circa 2500BC to 1500 BC