On the other hand, the ATF seems to think they were made in both calibers:
In the current AFT C&R publication the “OSS Glove Pistol, caliber.38 S&W or.38 special,” is listed under Section III as a weapon removed from the NFA list as collectors’ items and classified as a curio or relic under the GCA stating: “The Bureau has determined that by reason of the date of their manufacture, design, and other characteristics, the following firearms are primarily collector’s items and are not likely to be used as weapons and, therefore, are excluded from the provisions of the National Firearms Act.”