Existing glulam stamp Existing glulam stamp jwilson33 (Structural) (OP) 14 Nov 08 14:15 Is there any signficance to a stamping on an existing glulam that says something like "P-149 proof load tested". RE: Existing glulam stamp ThePioneer (Structural) 24 Nov 08 11:04 P-149 will be the identification of the manufacturer. Plant #149 as licensed by the American Institute of Timber Construction (www.aitc-glulam.org).It took a while, but I dug out some old records. P-149 was the Weyerhaeuser Company plant at Cottage Grove, Oregon. This operation was closed down in 1992.Proof loaded indicates that the end joints (most likely finger joints) were proof loaded during the manufacturing process to indicate they met whatever loading was specified for that particular member.AndreasSentinel Structures, Inc.