Okay here is a most basic script
so basically you can run this script on any adobe cc product as far as I'm concerned but you don't even need it at all. just install ExendScript Toolkit from here, paste below code in estk and just click on that green play icon and it should work too if you don't have PS AI etc. but if you have photoshop then you can just save below code as "Anyname.jsx" and later from "File-Scripts-Browse" you can run the script too.
So main prerequisite are as following : Make sure you have only "png" files in your folder! and I assume your PNG sequence starts from 1200_00 (1st file must be 0 numbered else script won't work as you want! because it's just basic and needs much improvements)
Okay once you run the script you'll have to select the folder in which you have those images; and then once folder is selected then it will be asked to enter prefix (1200_) in your case; and then you can simply enter the file numbers like (5 and new folder will created with 5 images etc.) watch gif for more details :D
var x = Folder.selectDialog("","");
var z = x.getFiles ("*.png");
var fileLength = z.length;
var finalLength = fileLength;
var pattern = prompt ("What is your file pattern?", "", "Pattern");
var startcount = 0;
for(var i=0; i<fileLength; i++){
var segment = prompt(finalLength + "files left; how much file you want to proceed?","","Enter File Numbers");
if(parseInt(segment) > finalLength){
alert(finalLength + "Files Left");
segment = prompt("Enter less than" + finalLength,"","Final Chance");
}
var endcount = startcount + parseInt(segment);
var value = parseInt(segment);
finalLength = finalLength - value;
main(startcount, endcount);
if(finalLength<=0) break;
}
function main(start, end){
var count = end - start;
var newFlder = new Folder (x + "/" + pattern + startcount);
if(!newFlder.exists){
newFlder.create();
}
for(var j=0;j<count;j++){
var file = z[startcount];
var trans = file.copy(newFlder + "/" + pattern + startcount + ".png");
startcount = startcount + 1;
}
}