In response, we have:

1. Archived the series by marking them as "discontinued" in their metadata, and by segregating in the catalog. Figures are percent rate (%), not seasonally adjusted (NSA). The series start as early as November 1946 and end as late as November 2017. 
2. Refurbished the catalog.

The series reside in the historical catalog (Canada » Financial » Interest rates » By frequency » Monthly) and are:

• BA%FMSFCSBUM.ICAN   = First coupon of Canada Savings Bond, (%)
• BA%FMSRMLR5YUM.ICAN = Average residential mortgage lending rate - 5 year, (%)
• BA%FMSFPD1MUM.ICAN  = Forward premium or discount - United States dollar in Canada: 1 month, (%)
• BA%FMSFPD3MUM.ICAN  = Forward premium or discount - United States dollar in Canada: 3 month, (%)
• BA%FMSCD3MSTUM.ICAN = Covered differential - United States 3 month short-term paper, (%)

Because catalog locations are subject to change, the upper-right search box on DataBuffet.com provides a "find in catalog" mode that accepts a mnemonic.

Please be aware that

• Canada Savings Bonds are no longer sold.
• Replace BA%FMSRMLR5YUM.ICAN with MB%MLR5YUM.ICAN, reported by CMHC.
• The Canada-US forward exchange rate and covered differential are based in part on the CAD-USD exchange rate, whose reporting changed in May 2017 (see related article). The covered differential is the exchange rate less the forward rate.

References

• Canada Savings Bond program