When you have three posts up you can use the PM system. If you hover your cursor over my name to the left of this post you'll see a 'send message' envelope. Send me your proper email address and I'll deal with the bulk of the RGA aspect with you.
Enlistment into this unit for numbers around him is end October 1915. This means he will have a number previous to the six digit one and the best I can narrow it down is to between 917 and 927 inclusive* You may have this number on some of his material.
Re RWF TF. On the assumption that he would have been in his local battalion, the 6th Bn, and going with the info that he had pre war service & was in service at outbreak then his number would have been no higher than around
1200. Plenty of 4th August men enlisting from around this number onwards. This number would not be on the medal card as that only denotes the mans number when posted overseas/theatre of war. He could have moved between any number of units and not be on the medal card.
The 6th Battalion had a second line formed and then a third line.
(re 2nd 6th- ignore the formed Carmarthen bit, it's Carnarvon. This error keeps being perpetuated regardless of efforts made to rectify it.)
Do you have any placenames in amongst any of his material? The 2nd line were also known to have been at Aberystwyth in early 1915.
No doubt you have had a look for his papers and come to the same conclusion as I have which is that his do not seem to have survived. If there's a suggestion that he continued/re- enlisted service in the Artillery TA after the war then his papers may be at the MoD. His number then would be a seven digit one* with the local one being the 61st Medium Bde (may
have been 12th for a short while) with many numbers starting 166xxxx.
You say you have his medals. Do you have a Territorial Force Efficiency Medal?
See bottom of this page
Lastly, may I suggest you post the photo of him with the RWF badge. There some on here who are hot on identifying uniforms and may be able to date it.
* All TF were renumbered to six digits in early 1917