Will you always see ejector markings on spent casings fired by a semi-automatic pistol?

No, you will not always see ejector markings on spent casings fired by a semi-automatic pistol. Ejector markings are typically left on casings by the ejector mechanism as they are expelled from the firearm. However, factors such as the condition of the ejector, the ammunition used, and the ejection pattern of the pistol can all affect whether or not markings are present on the casings.