diff --git a/Swift-Windows.md b/Swift-Windows.md
index f19fee8..75377c6 100644
--- a/Swift-Windows.md
+++ b/Swift-Windows.md
@@ -215,6 +215,33 @@ To connect this action to your button, you can either edit the XML, or use the m
 
 Alternatively, you can `Ctrl`-and-drag from the button's **Button Cell** to the **First Responder** you'll find under **Placeholders**, and select your function `clickClick:` from the list that appears.
 
+### D. Displaying the build version number
+
+In LunaMac version 1.4.3, I updated the About window to dynamically display the current build number, which is set in `Info.plist`. To make this slightly easier, and because Xcode offers no way to assign unique, meaningful names to window elements, we're first going to set the `Tag` property of the "Using LunaMac" text label to `100`.
+
+I've seen advice against using tags to identify form elements, but it's consistent and predictable, so I'm sticking with it. Note that the `Tag` property must be an **integer**, so you'll have to keep track of your tag numbers if you decide to use this method in your own projects.
+
+To programmatically access this label and set its value, we're going to update our `viewDidAppear()` function in `ViewController.swift`.
+
+We can retrieve the build version from the global `Bundle` object, using `Bundle.main.appBuild`.
+
+```swift
+override func viewDidAppear() {
+	...
+	if (title.contains("Changelog")) {
+		...
+	}
+	else if (title.contains("About")) {
+		// set label with version number
+		if (label.tag == 100) {
+			label.stringValue = ("Using LunaMac " + Bundle.main.appBuild)
+		}
+	}
+}
+```
+
+Launch your application and open the About window, and you'll see the current version number displayed.
+
 Now we need to make a changelog dialog, and the code to load it and its contents.
 
 ## III. The Changelog window