Hi Taylor,
I think you misguide to see the EGSM and PGSM both. But it both are GSM
900 only. Just for knowledge check the following bands too.

1.
GSM 450 Band:
For GSM 450, the system is required to operate in the following band:
450.4 MHz to 457.6 MHz: mobile transmit, base receive;
460.4 MHz to 467.6 MHz base transmit, mobile receive.

2.
GSM 480 Band:
For GSM 480, the system is required to operate in the following band:
478.8 MHz to 486 MHz: mobile transmit, base receive;
488.8 MHz to 496 MHz base transmit, mobile receive.

3.
GSM 850 Band:
For GSM 850, the system is required to operate in the following band:
824 MHz to 849 MHz: mobile transmit, base receive;
869 MHz to 894 MHz: base transmit, mobile receive.

4.
Standard or primary GSM 900 Band, P-GSM:
For Standard GSM 900 band, the system is required to operate in the
following frequency band:
890 MHz to 915 MHz: mobile transmit, base receive;
935 MHz to 960 MHz: base transmit, mobile receive.

5.
Extended GSM 900 Band, E-GSM (includes Standard GSM 900 band):
For Extended GSM 900 band, the system is required to operate in the
following frequency band:
880 MHz to 915 MHz: mobile transmit, base receive;
925 MHz to 960 MHz: base transmit, mobile receive.

6.
Railways GSM 900 Band, R-GSM (includes Standard and Extended
GSM 900 Band):
For Railways GSM 900 band, the system is required to operate in the
following frequency band:
876 MHz to 915 MHz: mobile transmit, base receive;
921 MHz to 960 MHz: base transmit, mobile receive.

7.
DCS 1 800 Band:
For DCS 1 800, the system is required to operate in the following
band:
1710 MHz to 1 785 MHz: mobile transmit, base receive;
1805 MHz to 1 880 MHz: base transmit, mobile receive.

8.
PCS 1 900 Band:
For PCS 1 900, the system is required to operate in the following
band:
1850 MHz to 1 910 MHz: mobile transmit, base receive;
1930 MHz to 1 990 MHz base transmit, mobile receive.

Feel free to ask.

Aloha,
Saurabh

FCC regulations.

In the US the Federal Communications Commission (FCC) does not allow
modifications to transmitters without testing and approval. While doing
a one off wouldn't require that you go through ALL the hoops, there
would be enough to make it more expensive and inconvenient than the
nostalgia would likely be worth.

Because current FCC regulations prohibit anyone other than those
specically authorized from modifying mobile phones. It violates the
type acceptance. It also prevents cloning of AMPS phones.

[snip]

Because messing with radio transmitters unless you are authorised to do so
is illegal. In the UK it comes under the Wireless Telegraphy Act. In the
US the FCC have similar legislation in place, but I don't know offhand
what it's called. It's why you need to take an exam to hold a radio
amateur licence.

Ivor