Script to select multiple objects that are all sized the same

with the limited information available, i was forced to make some assumptions. but this should do what you want, or at least give you the tools to edit it to do what you want.

This selects all items that have a "Registration" fill color, then it checks all the selected items to see if they're smaller than a maximum size, or larger than a minimum size.

https://github.com/wdjsdev/public_illustrator_scripts/blob/master/get_registration_marks.js

/*
	Script Name:
		Get Registration marks
	
	Script Description: 
		Select all items using the registration fill color. 
		Loop selected items to determine if they meet min/max size criteria
		Selected items that meet criteria are moved to registration layer
		Selected items that do not meet criteria can be deleted or ignored

	Author: 		 	
		William Dowling
		Email: 				illustrator.dev.pro@gmail.com
		Github:				github.com/wdjsdev
		Paypal:				paypal.me/illustratordev
	
	Forum Post: 
		https://community.adobe.com/t5/illustrator-discussions/script-to-select-multiple-objects-that-are-all-sized-the-same/td-p/12460743

	Github Repo:
		https://github.com/wdjsdev/public_illustrator_scripts/blob/master/get_registration_marks.js
	


*/


function getRegMarks()
{
	// set up the script and declare some variables
	var doc = app.activeDocument;
	var layers = doc.layers;
	var swatches = doc.swatches;
	var regSwatch = swatches["[Registration]"];

	// deselect all and then select all items that are filled with [Registration] color
	doc.selection = null;
	doc.defaultFillColor = regSwatch.color;
	app.executeMenuCommand("Find Fill Color menu item");

	// check to see whether any items were selected.
	// if not, alert the user and exit.
	var sel = doc.selection;
	if (!sel.length)
	{
		alert("No registration marks found.");
		return;
	}

	// if we've gotten this far that means registration marks have been successfully
	// selected. now let's create a new layer to copy them to. 
	var myRegMarksLayer = layers.add();
	myRegMarksLayer = "Registration";
	// You can also target
	// an existing layer by name instead of creating a new one.
	// to use an existing layer, you can get it like this:
	// var myRegMarksLayer = layers["Registration"]; // just enter the name of the layer you want between the brackets



	// here we set a variable to determine whether a selected object is
	// the correct size. Let's say your registration circles are 50pt in
	// diameter and your other mark that you need to delete is 25pt wide/tall
	// if we set the minimum size variable to, say, 45pt, then we can check
	// the dimensions of each selected piece to see if it meets the minimum size
	// requirement. any pieces that do not meet the requirement can be deleted or ignored.

	var minimumSize = 45; // use this line if you only want items that are at least this big
	// var maximumSize = 50; // use this line if you only want items that are at MOST this big.


	for (var s = sel.length - 1; s >= 0; s--)
	{
		// now, let's check to see if the current selected item
		// meets the min/max criteria set above
		// i'm assuming we're just checking width here. but
		// you can change this to height if you want, or you could
		// get some information about the area of the object
		// if that is more useful.

		if (sel[s].width >= minimumSize)
		{
			sel[s].moveToBeginning(myRegMarksLayer);
		}
		else
		{
			// choose what to do here.. you can ignore it.. 
			// or you can delete it. if you want to ignore it,
			// just comment the next line.
			sel[s].remove();
		}
	}
}
getRegMarks();