Stamp collecting, also known as philately, can be both a fascinating hobby and a lucrative investment. Greek stamps from the periods 1917, 1927 and 1932 can be particularly valuable depending on their condition, rarity and historical context. Here are some factors to keep in mind when assessing the value of these stamps:

### Factors that influence the value of stamps
1. **Condition**: Unused stamps in excellent condition are generally worth more than used ones. A stamp without tears, stains or faded colors has a higher collector's value.
2. **Rarity**: Stamps that are issued in limited editions or that are special because of a specific historical event can be considerably more valuable.
3. **Historical context**: Stamps issued during important periods in Greek history, such as the First World War (1914-1918) or the economic and political changes of the 1920s and 1930s, can have additional meaning and value.
4. **Original Value**: The face value of the stamp, indicated on the stamp itself, may also play a role, although this is less important than the above factors.

### Specific Greek Stamps
- **1917**: During the First World War there were several issues of postage stamps in Greece. It is useful to look at stamps with special overprints or those issued during military occupations.
- **1927**: During this period there may be stamps relating to national commemorations or economic reforms. For example, the commemoration of the Greek War of Independence may have had important issues.
- **1932**: This year came at a time of economic crisis and political unrest in Greece. Stamps from this period can be rare and valuable, especially if they mark a particular event or were printed in a limited edition.

### Rating and Sales
To determine the exact value of your stamps, it is advisable to:
- Consult a catalogue, such as the Michel or Scott catalogue, which provides detailed information on stamps and their estimated values.
- Seek advice from a recognized philatelist or an auction house specialized in stamps. They can provide a professional appraisal.
- Have the stamps certified, especially if they are rare or in exceptional condition.

### Conclusion
Owning Greek stamps from 1917, 1927 and 1932 can form a valuable collection. By using the right resources and expertise, you can gain a better understanding of their historical and financial value.