To understand the origins of these scarce and beautiful stamps, it is necessary to know about the Lambert Sales Co. In the mid-1920s, the Lambert family was socially, politically and economically influential on both sides of the Pacific Ocean. United States operations of the firm were located in New York City and run by Leon Lambert Sr., while Leon Lambert Jr. was in charge of the company's operations in Manila. The company manufactured fancy baby apparel in the Philippines for export to the United States, taking advantage of reduced manufacturing costs in the islands. Finished clothing was shipped to company headquarters in New York for distribution to United States department stores.

The cost of shipping in such an operation was quite substantial, even by the standards of the day. Prior to 1925 the company used regular Philippines issues to pay the postage, which sometimes amounted to thousands of Philippine pesos each month. Concerned about internal thefts of stamps, the Lambert Sales Co. asked Philippine postal authorities for permission to apply a special "L.S.C." perfin cancellation that would serve to earmark company postage and deter potential thieves. The idea was rejected, as it would have defaced the portraits of the men honored on the stamps, and the company sought another answer. The Bureau of Engraving and Printing in Washington, D.C., suggested a simple solution: an issue identical in design to the current definitives, but easily distinguished from them by virtue of being imperforate.

The BEP offered to produce such stamps for any Philippine company that would commit to a minimum order of 10,000 pesos in postage. The Lambert Sales Co. was the only one- to place such an order, contracting for postage in the amount of 10,180p. The  Philippine  Bureau  of Posts increased the Lambert Co. order so that copies of the imperforate stamps could be placed on sale at the Manila post office, presumably to satisfy stamp collectors. It is believed that Leon Lambert Jr. felt that it was critical to control all the imperforate stamps as an absolute defense against pilferage. Apparently, Lambert asked to be informed when the portion of the imperforate order destined for the Manila post office arrived. He then simply went to the post office and purchased the entire remaining imperforate stock.

Table of the Philippine imperforate issues of 1925 and the imperforate reprints of 1931.

As a result, few stamps if any from the original imperforate printing were sold by the post office directly to collectors. Some short sets of the 2-centavo through the 30c denominations were given to personal friends of the Lambert family. The result of all this is that virtually all used copies of the 1925 imperforate issues are found on, or were removed from, Lambert Sales Co. package labels on its shipments to New York.

The surviving stamps and labels from what was initially a very limited printing present plenty of challenge for even the most diligent collector. It is believed that about 15 percent of the original labels were saved, and perhaps as few as one in 10 of the used stamps from these labels are still sound.