This MacGregor 4BB brassie has a large circular ivory insert surrounded by red and black fiber, a brass soleplate, and a brass backweight. The shaft measures 41 !/2” and retains its original leather grip. MacGregor’s 1917 catalog advertised Model 4 woods.  Besides noting that they came with a “Russia Calf Grip” and “second growth hickory' shaft,” the catalog states the Model 4 includes:

“Another new design in which the ivory insert, an inch in diameter and 7/8 inch in depth, is encased in cylindrical fibre wall, securely fastened to the pin-locked fibre face.

“This double wall, allowing for all possible expansion and contraction affords the best protection to the ivory of any club of this character that has yet been put on the market. A "distance face" club that combines great distance driving with extreme durability.”

This insert, which is on the brassie offered here, was patented in 1919 by George Mattern of Dayton, Ohio.

Crawford, McGregor & Canby first sold woods with ivory inserts in 1912. Their 1913 catalog advertised these woods as the “ ‘J. MacGregor’ Genuine Ivory Face Drivers and Brassies.” They used the Hubbell insert patented in 1909, but included two fiber dowels advertised as “fibre lock pins.” The 1913 catalog description for these clubs reads in part:

“Used by Charles (Chick) Evans and many other prominent golfers. The J. MacGregor Ivory Face Clubs have made a big hit the past year. They are perfect in balance and conform to all the laws of motion required in a classy club. The Ivory is inserted in a circular form. The perfect joint being reinforced by our improved fibre lock pins. The Ivory face lengthens the drives of the moderate.”

For more see TCA2 v2 p408.