Sam, Yes the horse does not have his winter coat, but he is also not totaly slicked out. Here are some factors that come into play on a horse shedding his winter coat. What kind of winter did he go through, was it a harsh or mild winter and was it an early or late spring. Did he have enough feed and forage over the winter and this horse looks ok here. Next the age and over all health of the animal will determine how it comes out of a winter and like I said before his muscle tone looks good. And finally there is the maintenace, a horse was the automobile of its day. If you don't maintain a car you have problems and if you don't maintain a horse you have problems. The food and shelter is a given. I've looked and I can't tell if this horse is shod or not. Now back to the winter coat a horse needs to be curry combed and brushed out year round, but in the spring at the first sign of shedding you want all that loose hair off as soon as possible especially if the horse is ridden very much. Leaving that loose shag of hair on his back along with sweat, a saddle and a lot of riding, remember these horses were the mode of transporation of the day. Not keeping the horse clean and free of winter shag you ran a risk of galling his back or the girt and cinch area. This is not good and as we say "the horse might go a little WESTERN with ya". So what I'm saying is the winter coat needs to go as soon as it starts turning loose.
I've e-mailed a buddy of mine he's a head movie wrangler and stuntman and raises horses near Richmond, Virginia. I want to see what he has to say about his horses starting to loose their winter coats in the spring around the Richmond area.