The project must haves' are as follows.
DONE : *Fits in an area of 1 inch x 1 inch or (25.4mm x 25.4mm) Numitron Tube size: 32 x 10 mm (1.28 inch x 0.4 inch)
PROBABLY NOT : *Also compatible with HP bubble displays (4 digit 7 segment).
DONE : *at least 2 user buttons.
DONE : *an RTC DS1337
DONE MOSTLY (8Mhz) : *low power management running at 4~8Mhz
DONE (ATMEGA168) : *Atmel atmega line micro (looking at Attiny841 Micro).
DONE : *Serial interface.
DONE : *USB chargeable Libpo
DONE (300mF) : *Super cap backup for RTC.