Lol beefing up, I haven't heard that in a while Why is it that you need to beef him up?
If you can post a picture of your Greek, we can help you figure out his subspecies, and Danny will definitely be able to give an estimate of your torts age for you
What are you feeding him at the moment?
His is a T.G. Ibera according to the experts in "Greek Geeks'. At the vet check, the vet said she would like to feel more "heft" when she picks up a tortoise. We really don't have a lot of history on this little guy. His diet is everything that people have suggested here. Greens, opuntia, a bit of prickly pear, a bit of squash now and again, grass, flowers, sprinkled with TNT and the ultrafine calcium, no phosphorus with vit d. I have had this tortoise for 2 weeks now. He is very active, and seems content in his new home.
If you have a UVB lamp or he is outside in the sun I would not give him calcium with D3. What is his SCL? This along with his wt will tell us how much underweight he is if any. Glad to hear he is doing well it may just take some time to "beef" him up.
UVB lamp, I do not have an outdoor enclosure for him yet. It isn't that warm here. The weather may be nice atone moment, and the fog could roll in the next. Hate to take chances. He may be outside when I am home only! I will do an SCL today.
Try moistened Mazuri. That's what breeders do for rapid growth. I use it as a regular supplement. I am sure it would add weight, but you'd want to be careful to make sure the new growth was healthy.