There is only one file type that uses the .NMBTEMPLATE extension:
Numbers Spreadsheet Template
Spreadsheet template created by Numbers, an Apple iWork spreadsheet application; saves the layout and cell formatting of the one or more sheets in the workbook; often used to pre-populate the styles and equations required for logging work hours, tracking tasks, and preparing budgets.
NMBTEMPLATES can be created by choosing. After a Number template is opened, the spreadsheet can be saved to a .NUMBERS file.
Updated: October 21, 2015