John is correct.
Grumley did make some solid yew bows. I have several all yew Grumley bows. Many are straight end bows, two that I have are horn nock. One has the Pre-Bear Grumley brand, the others are branded "Bear Products by Grumley". Very few all yew Grumley bows have recurved tips.
Yew was also used as the core wood later on in most of the standard 3-Lamination Grumley bows. Most of his 3-Lam bows have a hickory back, yew core and osage belly.
When Grumley bows were still in the catalog, for $10 less you could order any of the standard bows with a lemonwood core and lemonwood belly rather then the yew core and osage belly.
While similar to a Grumley Bush Bow, judging from the small photographs, the bow in question is not an original Grumley.
Many bowyers imitated Grumley's bows. Perhaps the best Bush Bow imitation I have ever seen was made by Cliff Coe and has the best looking Coe marking on it that I have seen.
Pearl Drums - Yes, many Grumley bows were refinished by people who had no idea what they were doing and completely destroyed the artistic lines of Grumley's work. It is amazing how much damage a little sanding can do to an old all wood bow.
I have one solid osage Deerslayer that Nels Grumley refinished himself. It is perhaps the only refinished Grumley that I can think of that is equally desirable and valuable as an exact Grumley bow in all original condition.
I believe if I examined your bow in person, that I could easily tell if you bow is an original Grumley bow that someone refinished and in the process altered the lines.
You will have to bring the bow to Compton next June and we can compare it to several original Grumley bows that I will have there.