I am only adding this. I am sure you are aware of it. There is a memorial at Cardross. It is for WWI And WWII. There were soldiers listed. . The only names listed were those who were a casualty and I didn't see a Mc Culloch. He might have survived that is if he were even there.
I went to the internet. I listed the wrong war. "WWI Cardross Derby." I got a lot of different offerings; but what I did notice there was a street, town, or station name "Derby".
There were a lot of offerings; but I was looking for something more substantial. So I didn't trace it down. I couldn't find a Mc Culloch with that Regimental or Service Number. I was led into several different directions and did a search on Ancestry; but couldn't tie it into anything.
I found one sight . A Burrowhead; but I can't say for sure that it is tied into Cardross; but they required a fee.
There was a ship named Cardross also. Its just not a lot of info to go on. It seems that the Regimental No. might lead somewhere; but nothing for me. If I have some time. i will pursue it further.It also led meto Canada for some reason.
Try to see if that is Barrowhead, Burrowhead or maybe Barrancas. Could you possibly show us a copy or a photo of the helmet and the inside. I would appreciate it very much. Danny