Not sure which TPG, but MS65 seems to be the favorite on these and many commemoratives. Yours, I'd give MS63.
Pics really aren't good enough, but I'll venture a 65 because of the year/series (the '38 & '39's were sold as a PDS set primarily to collectors). So, 65 (with a 2% shot at 66 )
I don’t take slab grades very seriously. I sent a commem to PCGS a couple of years ago, and it came back Questionable Color.” I thought the color was fine, and I knew it hadn’t been recolored, as it had been in an album for about 30 years, having been put there by me as a fully white coin. I cracked it out a couple of months ago, resubmitted it raw, and it came back MS65.
By the way, if you own a GoldShield slab, it includes PCGS's TrueView. You can always pull up and download high res photos of your coin here: http://images.pcgs.com/trueview/34828898
Not arguing the grade, but looks weakly struck. Especially around the headset and rear of wagon. I am by no means an expert and only mention to get comments for my education.
Looking at the TrueViews, 66 makes sense. The strike on the rear of the wagon isn't as strong as it is on some issues, but seems to be typical for 38-D, even in higher grades.